Introduction of ports subdirectory where all ports are moved to

The main change in this release is the introduction of a "ports/"
subdirectory at the top-level of the repository, and all of the ports are
moved here.  In the process the "stmhal" port is renamed to "stm32" to
better reflect the MCU that it targets.  In addition, the STM32 CMSIS and
HAL sources are moved to a new submodule called "stm32lib".

The bytecode has changed in this release, compared to the previous release,
and as a consequence the .mpy version number has increased to version 3.
This means that scripts compiled with the previous mpy-cross must be
recompiled to work with this new version.

There have also been various enhancements and optimisations, such as:
check for valid UTF-8 when creating str objects, support for reverse
special binary operations like __radd__, full domain checking in the math
module, support for floor-division and modulo in the viper emitter,
and addition of stack overflow checking when executing a regex.

The stm32 port sees improved support for F7 MCUs, addition of a new board
B_L475E_IOT01A based on the STM32L475, and support for the Wiznet W5500
chipset along with improved socket behaviour.

A detailed list of changes follows.

py core:
- objstr: startswith, endswith: check arg to be a string
- nlrx86,x64: replace #define of defined() with portable macro usage
- objtype: handle NotImplemented return from binary special methods
- objtype: mp_obj_class_lookup: improve debug logging
- map: remove unused new/free functions
- make m_malloc_fail() have void return type, since it doesn't return
- modstruct: in struct.pack, stop converting if there are no args left
- modstruct: check and prevent buffer-read overflow in struct unpacking
- modstruct: check and prevent buffer-write overflow in struct packing
- nlrthumb: get working again on standard Thumb arch (ie not Thumb2)
- objfloat: fix binary ops with incompatible objects
- obj: fix comparison of float/complex NaN with itself
- objtype: implement fallback for instance inplace special methods
- objtuple: properly implement comparison with incompatible types
- objstr: add check for valid UTF-8 when making a str from bytes
- objlist: properly implement comparison with incompatible types
- runtime0.h: move relational ops to the beginning of mp_binary_op_t
- runtime0.h: move MP_BINARY_OP_DIVMOD to the end of mp_binary_op_t
- objtype: make sure mp_binary_op_method_name has full size again
- runtime0.h: put inplace arith ops in front of normal operations
- builtinhelp: simplify code slightly by extracting object type
- runtime: implement dispatch for "reverse op" special methods
- nlrx86: fix building for Android/x86
- builtinhelp: change signature of help text var from pointer to array
- runtime.h: change empty mp_warning macro so var-args are non empty
- modbuiltins: implement abs() by dispatching to MP_UNARY_OP_ABS
- {objfloat,objcomplex}: optimise MP_UNARY_OP_ABS by reusing variables
- mpconfig.h: add note that using computed gotos in VM is not C99
- objstr: strip: don't strip "\0" by default
- objexcept: prevent infinite recursion when allocating exceptions
- stream: remove unnecessary checks for NULL return from vstr_add_len
- vstr: raise a RuntimeError if fixed vstr buffer overflows
- vm: use lowercase letter at start of exception message
- persistentcode: define mp_raw_code_save_file() for any unix target
- add config option to print warnings/errors to stderr
- objfloat: support raising a negative number to a fractional power
- objset: simplify set and frozenset by separating their locals dicts
- objset: check that RHS of a binary op is a set/frozenset
- objset: include the failed key in a KeyError raised from set.remove
- objtype: change type of enum-to-qstr table to uint16_t to save space
- objstr: make empty bytes object have a null-terminating byte
- mpprint: only check for null string printing when NDEBUG not defined
- objtype: clean up unary- and binary-op enum-to-qstr mapping tables
- persistentcode: bump .mpy version number to version 3
- bc: update opcode_format_table to match the bytecode
- modmath: add full checks for math domain errors
- modmath: convert log2 macro into a function
- formatfloat: don't print the negative sign of a NaN value
- formatfloat: use standard isinf, isnan funcs instead of custom ones
- modbuiltins: use existing utf8_get_char helper in builtin ord func
- emitnative: implement floor-division and modulo for viper emitter
- objtype: use CPython compatible method name for sizeof
- objtype: fit qstrs for special methods in byte type
- objtype: define all special methods if requested
- objtype: introduce MICROPY_PY_ALL_INPLACE_SPECIAL_METHODS

extmod:
- modubinascii: only include uzlib/tinf.h when it's really needed
- modussl_mbedtls: allow to compile with MBEDTLS_DEBUG_C disabled
- machine_pinbase: put PinBase singleton in ROM
- re1.5: upgrade to v0.8.2, adds hook for stack overflow checking
- modure: add stack overflow checking when executing a regex
- uos_dupterm: update uos.dupterm() and helper funcs to have index
- uos_dupterm: swallow any errors from dupterm closing the stream
- vfs: replace VLA in proxy func with small, static sized array
- modussl: add finaliser support for ussl objects
- modussl_mbedtls: allow to compile with unix coverage build

lib:
- add new submodule, stm32lib containing STM32 CMSIS and HAL source
- embed/abort_: use mp_raise_msg helper function
- libm: fix tanhf so that it correctly handles +/- infinity args
- libm: remove implementation of log2f, use MP_NEED_LOG2 instead
- axtls: update, support for SSL_EAGAIN return code
- berkeley-db-1.xx: update, allow to override MINCACHE, DEFPSIZE

drivers:
- memory/spiflash: change from hard-coded soft SPI to generic SPI
- display/ssd1306.py: improve performance of graphics methods
- nrf24l01: make nRF24L01 test script more portable
- display/ssd1306: implement SSD1306_I2C poweron method
- display/ssd1306: make poweron() work the same with SSD1306_SPI
- wiznet5k: improve the performance of socket ops with threading
- wiznet5k: get low-level W5500 driver working

tools:
- upip: upgrade to 1.2.2
- pyboard: use repr() when quoting data in error messages
- pyboard: update docstring for additional device support

tests:
- object_new: better messages, check user __new__() method
- class_new: add checks for __init__ being called and other improvements
- class_new: add another testcase for __new__/__init__ interaction
- class_inplace_op: test for inplace op fallback to normal one
- run-bench-tests: update locations of executables, now in ports/
- class_reverse_op: test for reverse arith ops special methods
- run-tests: skip class_inplace_op for minimal profile
- run-tests: fix copy-paste mistake in var name
- cpydiff: add cases for locals() discrepancies
- extmod: add test for ure regexes leading to infinite recursion
- extmod: add test for '-' in character class in regex
- run-tests: close device under test using "finally"
- net_inet: update tls test to work with CPython and incl new site

unix port:
- rename modsocket.c to modusocket.c
- modusocket: remove #if MICROPY_SOCKET_EXTRA code blocks
- enable MICROPY_PY_REVERSE_SPECIAL_METHODS

stm32 port:
- modmachine: make machine.bootloader() work when MPU is enabled
- modmachine: improve support for sleep/deepsleep on F7 MCUs
- compute PLL freq table during build instead of at run time
- modmachine: for F7 MCU, save power by reducing internal volt reg
- boards/pllvalues.py: make script work with both Python 2 and 3
- Makefile: use lib/stm32lib instead of local cmsis and hal files
- remove cmsis and hal files, they are now a submodule
- Makefile: automatically fetch stm32lib submodule if needed
- update to new STM Cube HAL library
- fix clock initialisation of L4 MCUs
- rename stmhal port directory to stm32
- remove unused usbd_msc.c file
- boards: change remaining stm32f4xx_hal_conf.h to unix line ending
- boards: change linker scripts to use "K" instead of hex byte size
- boards: fix I2C1 pin mapping on NUCLEO_F401RE/F411RE boards
- i2c: when scanning for I2C devices only do 1 probe per address
- modnwwiznet5k: release the GIL on blocking network operations
- boards: add new board B_L475E_IOT01A based on STM32L475
- make-stmconst.py: make sure mpz const data lives in ROM
- timer: make pyb.Timer() instances persistent
- mpconfigport.h: add configuration for max periphs on L4 series
- usbdev: make the USBD callback struct const so it can go in ROM
- usbdev: change static function variable to non-static
- usbdev: put all CDC state in a struct
- usbdev: put all HID state in a struct
- usbdev: simplify CDC tx/rx buffer passing
- usbdev: simplify HID tx/rx buffer passing
- usbdev/core: add state parameter to all callback functions
- usbdev: put all state for the USB device driver in a struct
- usbdev: simplify pointers to MSC state and block dev operations
- usbdev: merge all global USB device state into a single struct
- usbdev: make device descriptor callbacks take a state pointer
- usbdev: move all the USB device descriptor state into its struct
- timer: enable ARPE so that timer freq can be changed smoothly
- modnwwiznet5k: get the IP address of an established socket
- boards: fix typos in stm32f767_af.csv table
- usbd_cdc_interface: don't reset CDC output buf on initialisation
- modnwwiznet5k: implement WIZNET5K.isconnected() method
- modusocket: make getaddrinfo() work when passed an IP address
- modusocket: return OSError(-2) if getaddrinfo fails
- mpconfigport.h: add MICROPY_THREAD_YIELD() macro
- modnwwiznet5k: add support for W5500 Ethernet chip
- modnwwiznet5k: increase SPI bus speed to 42MHz
- modnwwiznet5k: implement stream ioctl for the Wiznet driver
- mphalport: improve efficiency of mp_hal_stdout_tx_strn_cooked
- make uos.dupterm() conform to specs by using extmod version

cc3200 port:
- enable micropython.kbd_intr() method
- use standard implementation of keyboard interrupt

esp8266 port:
- rename axtls_helpers.c to posix_helpers.c
- posix_helpers: set ENOMEM on memory alloc failure
- set DEFPSIZE=1024, MINCACHE=3 for "btree" module
- esp_mphal: send data in chunks to mp_uos_dupterm_tx_strn
- modnetwork: add "bssid" keyword arg to WLAN.connect() method
- modules/webrepl_setup: add info about allowed password length

zephyr port:
- Makefile: revamp "test" target after ports were moved to ports/
- use CONFIG_NET_APP_SETTINGS to setup initial network addresses
- switch to interrupt-driven pull-style console

pic16bit port:
- add definition of SEEK_SET to unistd.h

docs:
- pyboard/tutorial: add "timeout=0" to UART in pass-through example
- more xrefs to "MicroPython port" in glossary
- library/network: fix ref to "socket" module (should be "usocket")
- machine.Signal: improve style/grammar and add usage example
- library: add description of "index" parameter to uos.dupterm()
- library/micropython: fix typo in RST formatting
- library/framebuf.rst: generalise constructor to all colour formats
- btree: describe page caching policy of the underlying implementation
- esp8266/tutorial: update neopixel with example of using 4 bbp
- library/network: clarify usage of "bssid" arg in connect() method
- pyboard/quickref: add info for Switch, RTC, CAN, Accel classes
- pyboard/tutorial: update now that yellow LED also supports PWM
- esp8266/quickref: add quickref info for RTC class
- library: add missing cross-ref links for classes in pyb module
- library/network: update docs to state that W5500 is supported
- uselect: document one-shot polling mode
- usocket: elaborate descriptions
- usocket: document inet_ntop(), inet_pton()
- library/network: add dhcp_hostname parameter
- reference/isr_rules: minor typo correction
- ussl: fix module name refs and use "MicroPython port" term
- esp8266/general: add section on TLS limitations
- usocket: document that settimeout() isn't supported by all ports
- ure: add "|" (alternative) to the list of supported operators
- reference/isr_rules.rst: add tutorial on use of micropython.schedule()

travis:
- use --upgrade when pip is installing cpp-coveralls
- update build command now that stm32 Wiznet config has changed

examples:
- hwconfig_console: add .on()/.off() methods

all:
- convert mp_uint_t to mp_unary_op_t/mp_binary_op_t where appropriate
- convert remaining "mp_uint_t n_args" to "size_t n_args"
- make new ports/ sub-directory and move all ports there
- update Makefiles and others to build with new ports/ dir layout
- remove inclusion of internal py header files
- use NULL instead of "" when calling mp_raise exception helpers

README:
- update "Dependencies" section
- add explicit section on contributing
- add gcc and arm-none-eabi-newlib to list of required components

.gitattributes:
- remove obsolete entries for stmhal/hal, stmhal/cmsis
- add entries for files that will move to ports/ dir

Double precision math library and support on pyboard, and improved ussl

This release brings general improvements and bug fixes to the core and
various ports, as well as documentation additions, clean-ups and better
consistency.  And effort has been made to clean up the source code to
make it more consistent across the core and all ports.

There is a new tool "mpy_bin2res.py" to convert arbitrary (binary) files
to Python resources for inclusion in source code (frozen or otherwise).

The ussl module has seen improvements, including implementation of
server_hostname (for axtls) and server_side mode (for mbedtls).

There is now a double-precision float math library and stmhal has support
to build firmware with software or hardware double-precision.

A detailed list of changes follows.

py core:
- formatfloat: fix number of digits and exponent sign when rounding
- modthread: raise RuntimeError in release() if lock is not acquired
- compile: raise SyntaxError if positional args are given after */**
- objint: support "big" byte-order in int.to_bytes()
- objint: in to_bytes(), allow length arg to be any int and check sign
- compile: fix bug with break/continue in else of optimised for-range
- compile: optimise emitter label indices to save a word of heap
- builtinimport: remove unreachable code for relative imports
- objnamedtuple: simplify and remove use of alloca building namedtuple
- mpprint: remove unreachable check for neg return of mp_format_float
- binary: add missing "break" statements
- runtime: mark m_malloc_fail() as NORETURN
- objstr: remove unnecessary "sign" variable in formatting code
- vm: make "if" control flow more obvious in YIELD_FROM opcode
- modmath: check for zero division in log with 2 args
- makeversionhdr.py: update to parse new release line in docs/conf.py
- objdict: factorise dict accessor helper to reduce code size
- change mp_uint_t to size_t in builtins code
- repl: change mp_uint_t to size_t in repl helpers
- compile: combine arith and bit-shift ops into 1 compile routine
- compile: use switch-case to match token and operator
- objgenerator: allow to hash generators and generator instances
- gc: refactor assertions in gc_free function
- vm: make n_state variable local to just set-up part of VM
- asmx64: support moving a 64-bit immediate to one of top 8 registers
- modmicropython: cast stack_limit value so it prints correctly
- builtinevex: add typechecking of globals/locals args to eval/exec
- py.mk: make berkeley-db C-defs apply only to relevant source files
- mperrno: allow mperrno.h to be correctly included before other hdrs
- mpz: make mpz_is_zero() an inline function
- implement raising a big-int to a negative power
- mkrules.mk: show frozen modules sizes together with executable size
- objtuple: allow to use inplace-multiplication operator on tuples
- objstr: raise an exception for wrong type on RHS of str binary op
- modsys: initial implementation of sys.getsizeof()
- binary.c: fix bug when packing big-endian 'Q' values
- add verbose debug compile-time flag MICROPY_DEBUG_VERBOSE
- binary: change internal bytearray typecode from 0 to 1
- objstringio: prevent offset wraparound for io.BytesIO objects
- objstringio: fix regression with handling SEEK_SET
- stream: seek: Consistently handle negative offset for SEEK_SET
- mkrules.mk: use "find -path" when searching for frozen obj files
- compile: remove unused pn_colon code when compiling func params
- objcomplex: remove unnecessary assignment of variable
- formatfloat: don't post-increment variable that won't be used again
- use "static inline" for funcs that should be inline
- asmthumb: use existing macro to properly clear the D-cache

extmod:
- modussl_axtls: update for axTLS 2.1.3
- modussl_axtls: implement server_hostname arg to wrap_socket()
- move modonewire.c from esp8266 to extmod directory
- modure: if input string is bytes, return bytes results too
- modubinascii: add check for empty buffer passed to hexlify
- modussl_axtls: allow to close ssl stream multiple times
- modussl_mbedtls: support server_side mode
- modussl_mbedtls: when reading and peer wants to close, return 0
- modframebuf: fix invalid stride for odd widths in GS4_HMSB fmt
- modussl_mbedtls: make socket.close() free all TLS resources
- modframebuf: consistently use "col" as name for colour variables
- modussl_mbedtls: implement non-blocking SSL sockets
- machine_signal: fix parsing of invert arg when Pin is first arg
- modframebuf: use correct initialization for .locals_dict
- modlwip: implement setsockopt(IP_ADD_MEMBERSHIP)
- modussl_mbedtls.c: add ussl.getpeercert() method
- modubinascii: rewrite mod_binascii_a2b_base64
- modubinascii: don't post-increment variable that won't be used
- modonewire: rename public module to mp_module_onewire
- for uos.stat interpret st_size member as an unsigned int
- use "static inline" for funcs that should be inline

lib:
- axtls: upgrade to axTLS 2.1.3 + MicroPython patchset
- libm/math: remove implementations of float conversion functions
- add libm_dbl, a double-precision math library, from musl-1.1.16

drivers:
- onewire: move onewire.py, ds18x20.py from esp8266 to drivers
- onewire: enable pull-up when init'ing the 1-wire pin

tools:
- gen-cpydiff: use case description as 3rd-level heading
- pyboard: add license header
- mpy_bin2res: tools to convert binary resources to Python module
- mpy-tool.py: don't generate const_table if it's empty
- mpy-tool.py: fix missing argument in dump() function

tests:
- net_inet/test_tls_sites.py: integration test for SSL connections
- net_inet: add tests for accept and connect in nonblocking mode
- basics: add tests for for-else statement
- net_inet: move tests which don't require full Internet to net_hosted
- connect_nonblock: refactor towards real net_hosted test
- auto detect floating point capabilites of the target
- import: add a test for the builtin __import__ function
- import: update comment now that uPy raises correct exception
- basics/namedtuple1: add test for creating with pos and kw args
- unix/extra_coverage: add test for mp_vprintf with bad fmt spec
- basics: add tests for arithmetic operators precedence
- cpydiff/modules_deque: elaborate workaround
- cpydiff/core_class_mro: move under Classes, add workaround
- cpydiff/core_arguments: move under Functions subsection
- cpydiff/core_class_supermultiple: same cause as core_class_mro
- cpydiff: improve wording, add more workarounds
- cpydiff: add case for str.ljust/rjust
- rename exec1.py to builtin_exec.py
- basics/builtin_exec: test various globals/locals args to exec()

minimal port:
- Makefile: enable gc-sections to remove unused code
- remove unused stmhal include from Makefile
- use size_t for mp_builtin_open argument

unix port:
- modtime: replace strftime() with localtime()
- mpconfigport.mk: update descriptions of readline and TLS options
- Makefile: disable assertions in the standard unix executable
- modjni: convert to mp_rom_map_elem_t
- for uos.stat interpret st_size member as an unsigned int

stmhal port:
- mpconfigport.h: remove config of PY_THREAD_GIL to use default
- make error messages more consistent across peripherals
- add initial implementation of Pin.irq() method
- add .value() method to Switch object, to mirror Pin and Signal
- move pybstdio.c to lib/utils/sys_stdio_mphal.c for common use
- add "quiet timing" enter/exit functions
- make available the _onewire module, for low-level bus control
- modules: provide sym-link to onewire.py driver
- boards/stm32f405.ld: increase FLASH_TEXT to end of 1MiB flash
- sdcard: allow a board to customise the SDIO pins
- add possibility to build with double-precision floating point
- boards: enable double-prec FP on F76x boards
- Makefile: use hardware double-prec FP for MCUs that support it
- Makefile: rename FLOAT_IMPL to MICROPY_FLOAT_IMPL to match C name
- Makefile: add CFLAGS_EXTRA to CFLAGS so cmdline can add options
- mpconfigport.h: allow MICROPY_PY_THREAD to be overridden
- boards: add configuration files for NUCLEO_F429ZI
- boards/NUCLEO_F429ZI: change USB config from HS to FS peripheral
- reduce size of ESPRUINO_PICO build so it fits in flash
- servo: make pyb.Servo(n) map to Pin('Xn') on all MCUs
- servo: don't compile servo code when it's not enabled
- use "static inline" for funcs that should be inline

cc3200 port:
- modusocket: simplify socket.makefile() function
- make non-zero socket timeout work with connect/accept/send
- modusocket: fix connect() when in non-blocking or timeout mode
- use the name MicroPython consistently in code

esp8266 port:
- Makefile: bump axTLS TLS record buffer size to 5K
- Makefile: allow FROZEN_DIR,FROZEN_MPY_DIR to be overridden
- Makefile: add LIB_SRC_C variable to qstr auto-extraction list
- make onewire module and support code usable by other ports
- modonewire: move low-level 1-wire bus code to modonewire.c
- modonewire: make timings static and remove onewire.timings func
- reinstate 1-wire scripts by sym-linking to drivers/onewire/
- move mp_hal_pin_open_drain from esp_mphal.c to machine_pin.c
- enable MICROPY_ENABLE_FINALISER
- README: make "Documentation" a top-level section
- machine_rtc: use correct arithmetic for aligning RTC mem len
- mpconfigport_512k: use terse error messages to get 512k to fit
- mpconfigport.h: make socket a weak link
- modesp: remove unused constants: STA_MODE, etc
- general: add known issue of WiFi RX buffers overflow
- use size_t for mp_builtin_open argument
- fix UART stop bit constants

zephyr port:
- Makefile: rework dependencies and "clean" target
- Makefile: revert prj.conf construction rule to the previous state
- remove long-obsolete machine_ptr_t typedef's
- Makefile: explicitly define default target as "all"
- modusocket: allow to use socketized net_context in upstream
- modusocket: socket, close: switch to native Zephyr socket calls
- modusocket: bind, connect, listen, accept: Swtich to native sockets
- modusocket: send: switch to native sockets
- modusocket: recv: switch to native sockets
- modusocket: fully switch to native Zephyr sockets
- modzephyr: add current_tid() and stacks_analyze() functions
- prj_base.conf: enable CONFIG_INIT_STACKS
- modusocket: update struct sockaddr family field name
- prj_96b_carbon.conf: re-enable networking on Carbon
- modzephyr: add shell_net_iface() function

docs:
- btree: add hints about opening db file and need to flush db
- select: rename to uselect, to match the actual module name
- license: update copyright year
- esp8266/tutorial/intro: discourage use of 512kb firmwares
- esp8266/tutorial/intro: Sphinx requires blank lines around literal blocks
- conf.py: include 3 levels of ToC in latexpdf output
- gc: mark mem_alloc()/mem_free() as uPy-specific
- gc: document gc.threshold() function
- builtins: list builtin exceptions
- conf.py: set default_role = 'any'
- lcd160cr: group related constants together and use full sentences
- ref/speed_python: update and make more hardware-neutral
- library/gc: fix grammar and improve readability of gc.threshold()
- move all ports docs to the single ToC
- topindex.html: remove link to wipy.io, it's no longer available
- conf.py: add .venv dir to exclude_patterns
- move topindex.html to templates/ subdir
- differences/index_template: use consistent heading casing
- builtins: add AssertionError, SyntaxError, ZeroDivisionError
- add glossary
- conf.py: switch to "new" format of intersphinx_mapping
- conf.py: add file for global replacements definition
- library: add CPython docs xref to each pertinent module
- replace.inc: add |see_cpython|, to xref individual symbols from CPython
- conf.py: set "version" and "release" to the same value
- *_index: drop "Indices and tables" pseudo-section
- pyboard: move hardware info into General Info chapter
- uerrno: document "uerrno" module
- esp8266/general.rst: fix name of NTP module
- pyboard: move info about using Windows from topindex to general
- uzlib: update description of decompress() and mention DecompIO
- pyboard/tutorial/amp_skin: add example for playing large WAV files
- library/ubinascii: update base64 docs
- library/usocket: move socket.error to its own section
- library/usocket: describe complete information on address formats
- glossary: elaborate on possible MicroPython port differences
- glossary: fix typos in micropython-lib paragraph
- index: rewrite introduction paragraph to avoid confusion
- use the name MicroPython consistently in documentation
- consistently link to micropython-lib in glossary

all:
- make more use of mp_raise_{msg,TypeError,ValueError} helpers
- unify header guard usage
- remove trailing spaces, per coding conventions
- don't include system errno.h when it's not needed
- use the name MicroPython consistently in comments
- make use of $(TOP) variable in Makefiles, instead of ".."
- raise exceptions via mp_raise_XXX
- make static dicts use mp_rom_map_elem_t type and MP_ROM_xxx macros

README:
- mention support for bytecode and frozen bytecode
- improve description of precompiled bytecode; mention mpy-cross

CODECONVENTIONS:
- clarify MicroPython changes sign-off process
- start to describe docs conventions
- describe docs use of markup for None/True/False

travis:
- build STM32F769DISC board instead of F7DISC to test dbl-prec FP
- pin cpp-coveralls at 0.3.12

Fixes for stmhal USB mass storage, lwIP bindings and VFS regressions

This release provides an important fix for the USB mass storage device in
the stmhal port by implementing the SCSI SYNCHRONIZE_CACHE command, which
is now require by some Operating Systems.  There are also fixes for the
lwIP bindings to improve non-blocking sockets and error codes.  The VFS has
some regressions fixed including the ability to statvfs the root.

All changes are listed below.

py core:
- modbuiltins: add core-provided version of input() function
- objstr: catch case of negative "maxsplit" arg to str.rsplit()
- persistentcode: allow to compile with complex numbers disabled
- objstr: allow to compile with obj-repr D, and unicode disabled
- modsys: allow to compile with obj-repr D and PY_ATTRTUPLE disabled
- provide mp_decode_uint_skip() to help reduce stack usage
- makeqstrdefs.py: make script run correctly with Python 2.6
- objstringio: if created from immutable object, follow copy on write policy

extmod:
- modlwip: connect: for non-blocking mode, return EINPROGRESS
- modlwip: fix error codes for duplicate calls to connect()
- modlwip: accept: fix error code for non-blocking mode
- vfs: allow to statvfs the root directory
- vfs: allow "buffering" and "encoding" args to VFS's open()
- modframebuf: fix signed/unsigned comparison pendantic warning

lib:
- libm: use isfinite instead of finitef, for C99 compatibility
- utils/interrupt_char: remove support for KBD_EXCEPTION disabled

tests:
- basics/string_rsplit: add tests for negative "maxsplit" argument
- float: convert "sys.exit()" to "raise SystemExit"
- float/builtin_float_minmax: PEP8 fixes
- basics: convert "sys.exit()" to "raise SystemExit"
- convert remaining "sys.exit()" to "raise SystemExit"

unix port:
- convert to use core-provided version of built-in import()
- Makefile: replace references to make with $(MAKE)

windows port:
- convert to use core-provided version of built-in import()

qemu-arm port:
- Makefile: adjust object-file lists to get correct dependencies
- enable micropython.mem_*() functions to allow more tests

stmhal port:
- boards: enable DAC for NUCLEO_F767ZI board
- add support for NUCLEO_F446RE board
- pass USB handler as parameter to allow more than one USB handler
- usb: use local USB handler variable in Start-of-Frame handler
- usb: make state for USB device private to top-level USB driver
- usbdev: for MSC implement SCSI SYNCHRONIZE_CACHE command
- convert from using stmhal's input() to core provided version

cc3200 port:
- convert from using stmhal's input() to core provided version

teensy port:
- convert from using stmhal's input() to core provided version

esp8266 port:
- Makefile: replace references to make with $(MAKE)
- Makefile: add clean-modules target
- convert from using stmhal's input() to core provided version

zephyr port:
- modusocket: getaddrinfo: Fix mp_obj_len() usage
- define MICROPY_PY_SYS_PLATFORM (to "zephyr")
- machine_pin: use native Zephyr types for Zephyr API calls

docs:
- machine.Pin: remove out_value() method
- machine.Pin: add on() and off() methods
- esp8266: consistently replace Pin.high/low methods with .on/off
- esp8266/quickref: polish Pin.on()/off() examples
- network: move confusingly-named cc3200 Server class to its reference
- uos: deconditionalize, remove minor port-specific details
- uos: move cc3200 port legacy VFS mounting functions to its ref doc
- machine: sort machine classes in logical order, not alphabetically
- network: first step to describe standard network class interface

examples:
- embedding: use core-provided KeyboardInterrupt object

New VFS subsystem and scheduling framework, and less need for the heap

This release adds some fundamental new components, allows for more Python
operations without using the heap and has reduced code size and stack
usage.

Changes in the way iterators are handled allows to iterate without
allocating on the heap for the types: tuple, list, str, bytes, bytearray,
array, dict, set, frozenset.  It also allows to call the builtins all, any,
min max and sum without allocating heap memory for the iterator argument.
And improvements to the handling of super() means that super().foo() method
calls are now heap-less.

A new generic VFS subsystem has been added which allows to mount arbitrary
filesystems (even written in Python) at the root or at a mount-point within
the root.  The FatFS driver has been replaced with an object-oriented
version (oofatfs) which allows a fully customisable filesystem layout.

A scheduling framework has been implemented in the core which gives the
ability to schedule callbacks to be called "as soon as possible".  This
allows ports to implement "soft IRQs" which allow the programmer to
allocate memory during an interrupt handler, at the cost of some
performance related to response time of the handler.  The new
micropython.schedule() function gives access to the scheduler.

Other improvements to the core include: consts can now be big-nums, for
example "X = const(1 << 100)"; addition of "help('modules')" to list
available modules; stack usage reduced for a Python call by 8 bytes on ARM
Cortex-M architectures; micropython.kbd_intr() function added to disable
Ctrl-C capture; addition of uio.resource_stream(); mpy-cross is built
automatically if needed; a helper tool mpy_cross_all.py is added to run
mpy-cross on an entire project.

The bytecode has changed in this version so existing .mpy files will need
recompiling.  There have also been some changes to the C API, most notably
with mp_uint_t changed to size_t in many places.

In the extended modules the following main changes have been made: addition
of machine.Signal class to allow inversion on a Pin; framebuf has new
formats of the form MONO_xxx; addition of uselect.ipoll() for allocation-
free polling; addition of uos.ilistdir() for efficient iteration of a
directory listing; machine.Pin high/low methods are renamed to on/off in
esp8266 and zephyr (this is a backwards-incompatible change);
machine.time_pulse_us() function no longer throws exceptions, but returns
negative values instead.

For stmhal the pyb.fault_debug() function is added, and default behaviour
for a hard-fault is now an immediate reset.  There is better support for F7
MCUs, in particular DMA and SD card support.  A bug has been fixed with the
USB VCP (USB serial) where it would in rare cases (usually when the host PC
was under load) would lose characters.  Pyboard now automatically mounts
all available partitions on the SD card.  Multithreading has been
implemented and is available via the _thread module, but this feature is
disabled by default and must be enabled at compile time using the
MICROPY_THREAD and MICROPY_THREAD_GIL options.  The ability to skip booting
from SD card is now available by creating an empty file on the flash called
"SKIPSD".

The cc3200 port has had some backwards incompatible changes, in particular
with I2C, Pin, UART and uos.  Please see the documentation for the new
behaviour.

The esp8266 port has had a change in the size of the firmware in order to
accommodate additional features.  As such the filesystem for this version
is incompatible with v1.8.7 and a device requires backup and erasure before
flashing this version.  Soft IRQs are now implemented for Pin and Timer
callbacks, along with the general improvements described above.

In the documentation there is now a section describing the differences
between MicroPython and CPython.  And code coverage is up to 98% across py/
and extmod/.

Changes in code size (in bytes) between v1.8.7 and this version are:

   bare-arm: -1104
    minimal: -1324
   unix x64: -1115
unix nanbox: -11106
     stmhal: +18116
     cc3200: +1032
    esp8266: +3060

Note that stmhal has increased significantly due to the addition of frozen
bytecode and the LCD160CR driver.

A detailed list of changes follows.

py core:
- builtinimport: raise ValueError for bad relative import, per CPython
- builtinimport: remove unreachable code and change obj-import comment
- runtime: refactor assert(0) to improve coverage
- runtime: fix handling of throw() when resuming generator
- objgenerator: when throwing an object, don't make an exc instance
- objgenerator: don't raise RuntimeError if GeneratorExit ignored
- parse: refactor code to remove assert(0)'s
- emitnative: remove assert(0)'s or replace with mp_not_implemented
- objexcept: replace if-cond and assert(0) with simple assert
- runtime: refactor default case of switch to remove assert(0)
- binary: mp_binary_get_size: Raise error on unsupported typecodes
- formatfloat: remove unreachable code
- objint_mpz: refactor switch-statement to remove unreachable default
- mpz: implement mpz_set_from_bytes() as a foundation for int.from_bytes()
- objint: from_bytes(): implement "byteorder" param and arbitrary precision
- objint_longlong: add stub for mp_obj_int_from_bytes_impl()
- add builtin help function to core, with default help msg
- move weak-link map to objmodule.c, and expose module maps as public
- builtinhelp: implement help('modules') to list available modules
- objint: fix left-shift overflow in checking for large int
- objmodule: move module init/deinit code into runtime functions
- objstr: optimize string concatenation with empty string
- showbc: make sure to set the const_table before printing bytecode
- py.mk: add CFLAGS_MOD flag to set config file for FatFs
- objstringio: allow to specify initial capacity by passing numeric argument
- objset: make inplace binary operators actually modify the set
- objfloat: raise ZeroDivisionError for 0 to negative power
- objcomplex: correctly handle case of 0j to power of something
- objset: fix inplace binary ops so frozensets are not modified
- added optimised support for 3-argument calls to builtin.pow()
- objstr: give correct behaviour when passing a dict to %-formatting
- mpconfig.h: move PY_BUILTINS_POW3 config option to diff part of file
- objstr: convert some instances of mp_uint_t to size_t
- objcomplex: fix typo in ternary expression
- asmxtensa.h: explicitly cast args to 32-bits so left-shift is legal
- map: change mp_uint_t to size_t where appropriate
- nlr: fix execstack builds for ARM
- objtype: add __delattr__/__setattr__ configured by MICROPY_PY_DELATTR_SETATTR
- emitbc: produce correct line number info for large bytecode chunks
- objtype: replace non-ASCII single-quote char with ASCII version
- modthread: use system-provided mutexs for _thread locks
- vm: add MICROPY_PY_THREAD_GIL_VM_DIVISOR option
- runtime: convert mp_uint_t to size_t where appropriate
- mpz: convert mp_uint_t to size_t where appropriate
- mpz: remove obsolete declaration of mpz_as_str_size
- mpz: change type of "base" args from mp_uint_t to unsigned int
- persistentcode: replace mp_uint_t with size_t where appropriate
- objtuple: convert mp_uint_t to size_t where appropriate
- objlist: convert mp_uint_t to size_t where appropriate
- objdict: convert mp_uint_t to size_t where appropriate
- objset: convert mp_uint_t to size_t where appropriate
- objstr: convert mp_uint_t to size_t (and use int) where appropriate
- objarray: convert mp_uint_t to size_t where appropriate
- objfun: convert mp_uint_t to size_t where appropriate
- objclosure: convert mp_uint_t to size_t where appropriate
- objexcept: convert mp_uint_t to size_t where appropriate
- objint: convert mp_uint_t to size_t where appropriate
- vm: convert mp_uint_t to size_t where appropriate
- add iter_buf to getiter type method
- allow bytecode/native to put iter_buf on stack for simple for loops
- make FOR_ITER opcode pop 1+4 slots from the stack when finished
- optimise storage of iterator so it takes only 4 slots on Py stack
- remove unused "use_stack" argument from for_iter_end emit function
- runtime: optimise case of identity iterator so it doesn't alloc RAM
- compile: optimise list/dict/set comprehensions to use stack iter
- de-optimise some uses of mp_getiter, so they don't use the C stack
- grammar: group no-compile grammar rules together to shrink tables
- lexer: don't generate string representation for period or ellipsis
- persistentcode: bump .mpy version due to change in bytecode
- lexer: simplify handling of indenting of very first token
- lexer: move check for keyword to name-tokenising block
- lexer: use strcmp to make keyword searching more efficient
- lexer: simplify handling of line-continuation error
- do adjacent str/bytes literal concatenation in lexer, not compiler
- lexer: convert mp_uint_t to size_t where appropriate
- grammar: remove unused rule
- objlist: for list slice assignment, allow RHS to be a tuple or list
- moduerrno: make uerrno.errorcode dict configurable
- moduerrno: make list of errno codes configurable
- parse: allow parser/compiler consts to be bignums
- create str/bytes objects in the parser, not the compiler
- parse: simplify handling of errors by raising them directly
- runtime: mp_raise_msg(): Accept NULL argument for message
- objarray: disallow slice-assignment to read-only memoryview
- map: fix bugs with deletion of elements from OrderedDict
- move locals/globals dicts to the thread-specific state
- nlr.h: mark nlr_jump_fail as NORETURN
- nlrxtensa: convert from assembler to C file with inline asm
- nlrx64: convert from assembler to C file with inline asm
- nlrx86: convert from assembler to C file with inline asm
- py.mk: force nlr files to be compiled with -Os
- modsys: use MP_SMALL_INT_MAX for sys.maxsize in case of LONGINT_IMPL_NONE
- runtime.c: remove optimization of '*a,=b', it caused a bug
- use mp_obj_get_array where sequence may be a tuple or a list
- nlrx86: add workaround for Zephyr
- nlrx64: fixes to support Mac OS
- objint_longlong: implement mp_obj_int_from_bytes_impl()
- allow lexer to raise exceptions during construction
- objint: allow to print long-long ints without using the heap
- emitnative: use assertions and mp_not_implemented correctly
- emitnative: remove obsolete commented out code
- mpprint: fix int formatting so "+" is printed for 0-valued integer
- mkrules.mk: remove special check for "-B" in qstr auto generation
- objstr: fix eager optimisation of str/bytes addition
- reduce size of mp_code_state_t structure
- provide mp_decode_uint_value to help optimise stack usage
- objstr: use better msg in bad implicit str/bytes conversion exception
- add micropython.schedule() function and associated runtime code
- vm: don't release the GIL if the scheduler is locked
- bc: provide better error message for an unexpected keyword argument
- use size_t as len argument and return type of mp_get_index
- sequence: convert mp_uint_t to size_t where appropriate
- define and use MP_OBJ_ITER_BUF_NSLOTS to get size of stack iter buf
- lexer: remove obsolete comment, since lexer can now raise exceptions
- modmath: allow trunc/ceil/floor to return a big int if necessary
- objint: handle special case of -0 when classifying fp as int
- modbuiltins: for round() builtin use nearbyint instead of round
- modbuiltins: allow round() to return a big int if necessary
- objtype: use size_t where appropriate, instead of mp_uint_t or uint
- objnamedtuple: use size_t where appropriate, instead of mp_uint_t
- use mp_locals/mp_globals accessor funcs instead of MP_STATE_CTX
- remove MP_STATE_CTX, use MP_STATE_THREAD instead (it's an alias)
- objarray: use mp_obj_str_get_str instead of mp_obj_str_get_data
- nlrx86: better check for Zephyr (requires 1.7)
- obj: change mp_uint_t to size_t for mp_obj_get_array_fixed_n len arg
- vm: fix VM opcode tracing to print correct stack pointer
- compile: when compiling super(), handle closed-over self variable
- objmap: convert mp_uint_t to size_t
- use mp_raise_TypeError/mp_raise_ValueError helpers where possible
- lexer: simplify and reduce code size for operator tokenising
- compile: simplify syntax-error messages for illegal assignments
- shorten a couple of error messages
- compile: provide terse error message for invalid dict/set literals
- convert mp_uint_t to size_t for tuple/list accessors
- change mp_uint_t to size_t for mp_obj_str_get_data len arg
- objzip: convert mp_uint_t to size_t
- obj.h: make sequence grow more efficient and support overlapping
- objstr: use MICROPY_FULL_CHECKS for range checking when constructing bytes
- add very simple but correct hashing for float and complex numbers
- objint: consolidate mp_obj_new_int_from_float to one implementation
- raise a ValueError if range() step is zero
- objtuple: add support for inplace add (same as normal add)
- make sure that static emg-exc-buffer is aligned to size of mp_obj_t
- runtime: when init'ing kbd intr exc, use tuple ptr instead of object
- objint: extract small int value directly because type is known
- objint: use unsigned arithmetic when formatting an integer
- obj: clean up and add comments describing mp_obj_type_t struct
- optimise types for common case where type has a single parent type
- objfloat: add implementation of high-quality float hashing
- nlrsetjmp: add check for failed NLR jump
- gc: execute finaliser code in a protected environment
- modmicropython: add micropython.kbd_intr() function
- reduce str/repr precision of float numbers when floats are 30-bit
- objtype: mp_obj_new_super doesn't need to be public, so inline it
- compile: don't do unnecessary check if parse node is a struct
- compile: extract parse-node kind at start of func for efficiency
- compile: add COMP_RETURN_IF_EXPR option to enable return-if-else opt
- compile: don't do unnecessary check if iter parse node is a struct
- compile: refactor handling of special super() call
- add LOAD_SUPER_METHOD bytecode to allow heap-free super meth calls
- mpz: strip trailing zeros from mpz value when set from bytes
- mpz: in mpn_sub, use existing function to remove trailing zeros
- cleanup use of global DEBUG preprocessor definition
- modio: implement uio.resource_stream(package, resource_path)
- objint: in int.from_bytes, only create big-int if really needed
- modio: resource_stream: Implement "package" param handling
- binary: handle storing big-ints to all arrays types
- lexer: simplify lexer startup by using dummy bytes and next_char()
- mkrules.mk: add dependency of .mpy files upon mpy-cross
- lexer: process CR earlier to allow newlines checks on chr1
- modsys: update conditionals for code referencing sys.stdout
- objstringio: fix StringIO reads at or beyond EOF
- sequence: fix boundary errors when slicing with a negative step
- objrange: fix slicing of range when step of slice is negative
- mkenv.mk: use $(TOP) instead of ".." to reference tools, mpy-cross
- vm: fix bug with stackless mode and unwinding of exceptions
- vm: fix bug with unwind jump popping the iterator from a for loop
- emitbc: fix bug with BC emitter computing Python stack size
- mkrules.mk: fix auto-qstr generation when "make -B" is used
- objstringio: catch mp_uint_t overflow of stream position in write()
- move BYTES_PER_WORD definition from ports to py/mpconfig.h

extmod:
- modframebuf: optimize fill_rect subroutine call
- modframebuf: clip pixels drawn by line method
- modframebuf: add GS4_HMSB format
- vfs_fat: rework so it can optionally use OO version of FatFS
- rename vfs_fat_file.h to vfs_fat.h
- add generic VFS sub-system
- vfs_fat: rework to support new generic VFS sub-system
- vfs: add ability for VFS sub-system to import using VfsFat
- modlwip: add socket.readinto() method
- vfs: expose mp_vfs_mount_t type
- vfs_fat: use SECSIZE macro to determine FatFs sector size
- machine_signal: implement "Signal" abstraction for machine module
- vfs_fat: update to use FF_DIR instead of DIR
- vfs: expose lookup_path_raw as mp_vfs_lookup_path
- vfs_fat: remove MICROPY_READER_FATFS component
- vfs_fat: remove MICROPY_FSUSERMOUNT_ADHOC config option
- remove MICROPY_FSUSERMOUNT and related files
- vfs_fat: remove MICROPY_FATFS_OO config option
- merge old fsusermount.h header into vfs.h and vfs_fat.h
- vfs_fat: remove unused fatfs_builtin_open function
- vfs_fat: remove unused function fat_vfs_listdir
- vfs_reader: fix use of NLR by popping context
- vfs_fat.c: use explicit include path for timeutils.h
- machine_pulse: make time_pulse_us() not throw exceptions
- machine_spi: remove EVENT_POLL_HOOK from soft-SPI transfer func
- machine_signal: implement Signal .on() and .off() methods
- vfs: allow to mount a block device, not just a VFS object
- vfs: raise OSError(EEXIST) on attempt to mkdir a mount point
- vfs: allow to stat the root directory
- modlwip: add my copyright
- modurandom: use mp_raise_ValueError()
- modutimeq: make scheduling fair (round-robin)
- modutimeq: add peektime() function (provisional)
- vfs_fat: remove obsolete and unused str/len members
- vfs_fat: allow to compile with MICROPY_VFS_FAT disabled
- vfs: rewrite path lookup algo to support relative paths from root
- modframebuf: add support for monochrome horizontal format
- utime_mphal: don't exit/enter the GIL in generic sleep functions
- modlwip: use mp_obj_str_get_str instead of mp_obj_str_get_data
- vfs_fat: fix calculation of total blocks in statvfs
- moduselect: update to use size_t for array accessor
- update for changes to mp_obj_str_get_data
- modframebuf: make monochrome bitmap formats start with MONO_
- machine_signal: support all Pin's arguments to the constructor
- machine_signal: rename "inverted" arg to "invert", it's shorter
- moductypes: fix bigint handling for 32-bit ports
- crypto-algorithms/sha256: remove non-standard memory.h header
- moduselect: convert to MP_ROM_QSTR and friends
- moduselect: refactor towards introduction of poll.ipoll()
- moduselect: implement ipoll() method for alloc-free polling
- modlwip: getaddrinfo: Allow to accept all 6 standard params
- modlwip: ioctl POLL: Fix handling of peer closed socket
- vfs: allow a VFS to be mounted at the root dir
- vfs: implement mp_vfs_ilistdir()
- vfs_fat: replace listdir() with implementation of ilistdir()
- vfs: use MP_S_IFDIR, MP_S_IFREG consts instead of magic numbers
- vfs_fat_misc: remove dot-dirs filter since FatFS already does it

lib:
- utils: remove old pyhelp helper, replaced with py/builtinhelp.c
- utils/pyexec: only print help prompt if HELP feature is enabled
- oofatfs: add OO version of FatFS library
- fatfs: remove old fatfs library component, it's replaced by oofatfs
- oofatfs/ffconf.h: allow to configure FS_EXFAT option
- oofatfs/ffconf.h: add MICROPY_FATFS_NORTC option
- utils/pyexec: allow to compile when the uPy compiler is disabled
- utils/pyexec: refactor to put lexer constructors all in one place
- memzip: make lexer constructor raise exception when file not found
- utils/pyexec: fix bug with pyexec_file not setting flag for source
- libm: add implementation of nearbyintf, from musl-1.1.16
- netutils: update for changes to mp_obj_str_get_data
- utils/pyexec: update event-driven REPL to match non-event REPL

drivers:
- fix some minor spelling mistakes
- display: add driver and test for uPy LCD160CR display
- memory: add SPI flash driver, written in C
- display/lcd160cr: use correct variable in set_power()
- display/lcd160cr: fix bugs with lcd.get_pixel()
- display/lcd160cr: fix bug with save_to_flash method
- display/lcd160cr: add check that JPEG size is less than 65536
- nrf24l01: update to work on newer ports, using machine, utime
- display/lcd160cr: fix get_line method and enhance screen_dump
- display/lcd160cr_test: allow test to take orientation parameter
- replace deprecated Pin.high()/low() methods with .__call__(1/0)

tools:
- tinytest-codegen.py: blacklist heapalloc_str.py test for qemu-arm
- upip: update to 1.1.5. Better and more user-friendly error handling
- add gen-cpydiff.py to generate docs differences
- gen-cpydiff.py: set the Python import path to find test modules
- gen-cpydiff.py: configurable CPython and micropython executables
- tinytest-codegen: update for recent test renaming ("intbig" suffix)
- pyboard: tighten up Pyboard object closure on errors
- pyboard: add "exec" and "execpty" pseudo-devices support
- pyboard: execpty: Use shell=False to workaround some curdir issues
- pyboard: processPtyToTerminal: Add workaround for PySerial bug
- pyboard: provide more details when expected reply not received
- mpy-tool: make work if run from another directory
- upip: upgrade to 1.1.6, supports commented lines in requirements.txt
- upip: upgrade to 1.2
- mpy-tool.py: use MP_ROM_xxx macros to support nanbox builds
- mpy_cross_all.py: helper tool to run mpy-cross on the entire project
- mpy-tool.py: fix regression with freezing floats in obj repr C

tests:
- add feature check for "const" keyword and skip related tests
- update test suite to be compatible with CPython 3.6
- improve stream.c test coverage
- import: improve builtinimport.c test coverage
- improve frozen import test coverage
- update tests, and add new ones, for recent generator tweaks
- io: improve test coverage of io.BufferedWriter
- basics: improve runtime.c test coverage
- extmod: improve test coverage of ure module
- float: add test for assigning to attribute of complex number
- extmod/framebuf1: add test for no-op fill_rect
- micropython/opt_level: add test for opt_level 3
- misc/non_compliant: add test for inability to assign func attrs
- basics: add test for assignment of attribute to bound method
- add test for int.from_bytes() for arbitrary-precision integer
- heapalloc_int_from_bytes: test that int.from_bytes() can work w/o alloc
- add test for builtin help function
- basics/builtin_help: add test for help('modules')
- make sure special tests can be skipped as well
- extmod/framebuf4: add tests for GS4_HMSB framebuf format
- extmod/framebuf1: fix test for framebuf invalid constructor
- extmod: add test for ure debug printing when compiling a regex
- heapalloc_str: test for alloc-free string operations
- extmod: update vfs_fat tests for new OO FatFs library
- extmod/vfs_fat: update tests to work with new VFS sub-system
- extmod/vfs_fat_ramdisk: make it work on pyboard
- run-tests: skip frozenset tests if set literal syntax is not available
- basics/zip: make skippable
- thread: make thread_exc2 runable on baremetal
- thread: fix stack size test so tests run reliably on baremetal
- heapalloc_bytesio: test for BytesIO with preallocates space
- basics/set_binop: add tests for inplace set operations
- float: add tests for zero to a negative power
- split tests for 2- and 3-arg pow()
- basics/string_format_modulo: add more tests for dict formatting
- pyb: adjust tests so they can run on PYB and PYBLITE
- misc: add test for line number printing with large bytecode chunk
- add option to not clear MICROPYPATH when running tests
- run-tests: allow to skip tests using async/await keywords
- comprehension1, containment: split set tests to separate files
- builtin_dir: the most expected thing in sys is exit, test for it
- basic/[a-f]*: make skippable
- dict_fromkeys: revert to use reversed() to run in native codegen mode
- extmod: make tests skippable
- thread: replace busy waiting loops with a loop that sleeps
- thread: add stress-test for creating many threads
- gen_yield_from_close: use range() instead of reversed()
- basic/: make various tests skippable
- cmdline: update tests to pass with latest changes to bytecode
- cmdline/cmd_showbc: update to work with recent changes
- micropython: add test for iterating with the heap locked
- micropython/heapalloc_iter: add tests for contains and unpack
- cmdline: update cmd_parsetree test for changes to grammar order
- cmdline/cmd_parsetree: update to work with changes to grammar
- basics/string_join: add more tests for string concatenation
- heapalloc_exc_raise.py: heap alloc test for raising/catching exc
- cpydiff: add initial set of tests for uPy-CPython differences
- cpydiff: add a test for storing iterable to a list slice
- micropython: add test for consts that are bignums
- extmod: add test for machine.Signal class
- basics: add further tests for OrderedDict
- run-tests: check for big int availability and skip related tests
- basic: split tests into working with small ints and not working
- float/complex1: split out intbig test
- float2int*: suffix with _intbig, don't run on any other int type
- string_format_modulo2: split off intbig test
- basics/string_join.py: add test case where argument is not iterable
- basics/unpack1.py: test if *a, = b copies b when b is a list
- micropython/: split off intbig tests
- uctypes_array_assign_native_le: split off intbig part
- basic: make various tests skippable
- float: make various tests skippable
- extmod: add very basic feature test for ussl module
- extmod: add websocket tests
- dict_fromkeys: split out skippable part
- micropython: make uio-using tests skippable
- micropython/heapalloc_traceback: fix backtrace line # after refactor
- micropython/opt_level: clarify the expected output for opt_level == 3
- feature_check/int_big: rework "big int" detection
- basics/fun_error: split out skippable test
- extmod: rename websocket test to websocket_basic
- misc/: make few tests skippable
- extmod: add a test for core VFS functionality, sans any filesystem
- extmod/vfs_basic: add more tests for basic VFS functionality
- extmod: improve re1.5/recursiveloop.c test coverage
- improve binary.c test coverage
- basics/struct_micropython: add test for 'S' typecode in ustruct
- run-tests: re-instate skipping of doubleprec test on pyboard
- extmod/vfs_basic: unmount all existing devices before doing test
- extmod: improve tinfgzip.c test coverage
- micropython/viper_error: add more tests to improve coverage
- basics/string_format2: adjust comment now that tests succeed
- basics: add test for string module formatting with int argument
- basics: move string-modulo-format int tests to dedicated file
- basics/bytes_add: add tests for optimised bytes addition
- micropython: add tests for micropython.schedule()
- heapalloc_str: test no-replacement case for str.replace()
- float: add tests for math funcs that return ints
- float: add tests for round() of inf, nan and large number
- basics: add test for super() when self is closed over
- basics: add tests for list and bytearray growing using themselves
- run-tests: be sure to close Pyboard object on completion
- vfs_fat_fileio.py is too big to be parsed in 16K heap, split in 2
- extmod/vfs_fat_fileio*: improve skippability
- float/byte*_construct: skip on missing array module
- micropython/heapalloc_iter: improve skippability
- run-tests: introduce generic "minimal" target
- float: add tests for hashing float and complex numbers
- run-tests: update names of tests that may need skipping
- basics: add tests for raising ValueError when range() gets 0 step
- basics: add test for tuple inplace add
- extmod/utimeq1: improve coverage of utimeq module
- run-tests: search feature checks wrt to main script location
- run-tests: don't post-process CRASH result in any way
- micropython: add test for micropython.kbd_intr()
- add tests for calling super and loading a method directly
- basics: add tests for int.from_bytes when src has trailing zeros
- cpydiff/core_arguments: fill in cause/workaround
- cpydiff/core_function_userattr: clarify, fill in cause and workaround
- cpydiff/core_import_prereg: fill in cause and workaround
- io/resource_stream: add test for uio.resource_stream()
- cpydiff/core_import_path: test showing difference in package.__path__
- cpydiff/core_import_split_ns_pkgs: test for split namespace packages
- cpydiff/core_function_unpacking: fill in workaround
- extmod: add more tests for VFS FAT
- extmod: add some more VFS tests
- micropython: add test for int.from_bytes with many zero bytes
- move super-as-local test from cpydiff to basic tests
- basics: update array test for big-int with lL typecodes
- basics: add memoryview test for big ints
- basics/lexer: add lexer tests for input starting with newlines
- extmod: make some vfs tests fully unmount FSs before running
- extmod/vfs: update tests to reflect new ilistdir() method
- basics/lexer: add line continuation tests for lexer
- extmod/vfs_fat: add test for ilistdir of a non-existent directory
- extmod/vfs_fat_more: make skippable is uos is not available
- io/bytesio_ext: test read() after seek() past end of BytesIO object
- basics/list_slice_3arg: add more tests for negative slicing
- basics/builtin_range: add tests for negative slicing of range
- basics: add more tests for unwind jumps from within a try-finally

mpy-cross:
- main: move lexer constructor to within NLR handler block
- fix compiler detection for including windows/fmode.c
- Makefile: override undefine any inherited variables
- Makefile: guard "override undefine" by test for make feature

bare-arm port:
- main: move lexer constructor to within NLR handler block
- Makefile: change C standard from gnu99 to c99

minimal port:
- update frozentest.mpy file for new .mpy version
- add ability and description to build without the compiler
- main: move lexer constructor to within NLR handler block
- Makefile: change C standard from gnu99 to c99
- main: make Cortex-M vector table constant

unix port:
- coverage: move coverage #if guard back to top of file
- enable builtin help function in coverage build
- enable MICROPY_PY_BUILTINS_HELP_MODULES in coverage build
- switch to OO version of FatFS library
- get minimal version compiling again
- change to use new generic VFS sub-system in coverage build
- fatfs_port: include new oofatfs header
- mpconfigport.h: remove obsolete MICROPY_FATFS_VOLUMES config
- modos: remove VfsFat from uos module, it's now in uos_vfs module
- make stack be non-executable
- fix freedos port build problems
- main: properly handle MICROPYPATH starting with ':'
- moduselect: implement ipoll() method with no-allocation policy
- modmachine: add Signal class to machine module
- remove remaining, obsolete traces of GNU readline support
- moduselect: properly implement ipoll object iteration
- main: refactor to put lexer constructors all in one place
- use mp_handle_pending() in time.sleep()
- coverage: enable scheduler and add tests for it
- use mp_obj_str_get_str instead of mp_obj_str_get_data
- convert mp_uint_t to size_t for use of mp_obj_list_get
- convert mp_uint_t to size_t in alloc.c
- enabled high-quality float hashing in coverage build
- remove obsolete MICROPY_FATFS macro
- main: ignore SIGPIPE signal, instead make EPIPE arrive
- main: don't allow to specify too small heap size
- main: implement -m option for packages
- Makefile: enable frozen bytecode modules dir
- move upip to frozen bytecode dir
- Makefile: don't add frozen bytecode to minimal build
- add ilistdir in uos module
- use core-provided KeyboardInterrupt exception object

windows port:
- .gitignore: ignore VC.db and VC.opendb files from VS2015
- make msvc project file support any version from VS2013 to VS2017
- bring mpconfigport.h up-to-date with unix port
- README: convert to Markdown
- README: fix some typos and grammar
- README: add a note about stack usage for msvc
- use core-provided KeyboardInterrupt exception object
- msvc: add machine/pin-related sources to build
- msvc: remove directory with generated files when cleaning
- msvc: do not define DEBUG for debug builds
- msvc: rebuild all qstrs when mpconfig headers are modified
- msvc: workaround parser bug in older MSBuild versions

qemu-arm port:
- don't compile tests in "REPL" mode
- mpconfigport.h: enable MICROPY_PY_BUILTINS_POW3 option
- enable machine module and associated tests
- add basic uos module with generic VFS capabilities
- move lexer constructors to within NLR handler block

stmhal port:
- support PortG on STM32L476 and STM32L486
- fix wrong usage of gcc -print-libgcc-file-name
- fix USB HID receive not receiving the first packet
- implement ioctl for USB HID read
- implement SNAK/CNAK mechanism for USB HID receive
- convert to use builtin help function
- enable help('modules') feature
- add default frozen-bytecode directory and link lcd160cr driver
- fix examples in openocd configs to include addresses
- add ability to have filesystem stored on external SPI flash
- boards/STM32L476DISC: use external SPI flash for filesystem
- mpconfigport.h: reorganise the config options into groups
- usbd_msc_storage: use storage functions instead of disk ones
- convert to use VFS sub-system and new ooFatFs component
- fix name of automatically created boot.py
- moduos: remove duplicated chdir
- use LED constants from PYBv4 onwards
- set the FatFs partition number when initialising VFS object
- fix stack pointer initialisation for F411 and F429 boards
- README: add paragraph about building mpy-cross
- on boot, mount all available partitions of the SD card
- main: put /sd directory before /flash in sys.path
- pin: add C-level pin ioctl method
- modmachine: add machine.Signal type
- main: guard init_sdcard_fs with MICROPY_HW_HAS_SDCARD
- pendsv: fill in comments about what the stack contains
- initial implementation of multithreading, currently disabled
- main: use _estack value to initialise stack extents
- fix build issue when MICROPY_PY_THREAD is disabled
- mpconfigport.h: enable MICROPY_PY_BUILTINS_POW3 option
- on HardFault, print stack pointer and do a stack dump
- add pyb.fault_debug() function, to control hard-fault behaviour
- use MICROPY_EVENT_POLL_HOOK instead of __WFI where appropriate
- add ability to skip booting from SD card via /flash/SKIPSD file
- Makefile: drop use of -mabi=aapcs-linux; link libgcc by default
- boards: for STM32F411DISC, change I2C pin according to datasheet
- implement a proper thread scheduler
- use generic interrupt char code
- main: remove unnecessary header includes
- use mp_hal_delay_ms instead of HAL_Delay
- rename sys_tick ticks/delay functions to corresp. mp_hal ones
- modpyb: use utime ticks ms/us functions instead of custom ones
- modnwcc3k: add include for mp_hal_delay_ms
- mphalport: get ticks_cpu() working on F7 MCUs
- main: allocate flash's VFS struct on the heap to trace root ptrs
- enable micropython.schedule()
- pendsv: disable interrupts during a thread switch
- irq: shift IRQ priorities of TIM and EXTINT to be above PENDSV
- pybthread: allow interrupts to work during lock/unlock of mutex
- systick: make mp_hal_delay_ms release the GIL when sleeping
- boards: fix alt-func config for PA5 of STM32F767
- board: fix existing and add more pin defs for NUCLEO_F767ZI
- spi: clean and/or invalidate D-cache before SPI DMA transfers
- hal: for F7 MCUs, expose DMA_CalcBaseAndBitshift function
- dma: fix reinitialisation of DMA on F7 MCUs, following F4
- update to use size_t for tuple/list accessors
- update for changes to mp_obj_str_get_data
- spi: increase SPI transfer timeout, proportional to num bytes
- support SDMMC alternate functions in pin generation
- sdcard: add support for SDMMC2 on F7 MCUs
- boards: update F76x alternate function table to add SDMMC2
- boards/STM32F769DISC: get SD card working by using SDMMC2
- boards/STM32F769DISC: fix user switch pin, and document stlink
- boards: remove F769 alt function table, it's same as for F767
- dma: don't include SDMMC2 struct if SDMMC2 is not available
- move L4/F7 I2C timing constants from mpconfigboard.h to i2c.c
- i2c: clean the cache so that I2C DMA works on F7 MCUs
- usbd_cdc_interface: increase in-endpoint timeout to 500ms
- usbd_cdc_interface: change CDC RX to use a circular buffer
- enable parsing of all Pin constructor args by machine.Signal
- timer: clear interrupt flag before setting callback
- convert all module and method tables to use MP_ROM macros
- modmachine: add machine.UART class, linking to pyb.UART
- modmachine: remove TODO comment that is now implemented
- add machine.Pin on/off methods
- add ilistdir in uos module

cc3200 port:
- convert to use builtin help function
- add implementations of mp_import_stat and builtin_open
- modusocket: remove deprecated socket.error
- convert to use new VFS sub-system and new ooFatFs library
- refactor "ticks" functions to use common extmod implementation
- move stoupper to ftp.c and define in terms of unichar_toupper
- use simplelink API instead of emulated BSD API
- remove util/std.h, can just use stdio.h instead
- mods/modwlan: remove unused header includes; simplify others
- mods/modwlan: make multi-threaded a proper compile-time option
- mods/modwlan: allow antenna diversity to be fully compiled out
- mods/modwlan: add int casts to silence compiler warnings
- remove remaining references to std.h
- move wlan socket glue functions from modwlan to modusocket
- convert to using uPy internal errno numbers
- when raising OSError's use MP_Exxx as arg instead of a string
- enable uerrno module with short, custom list of error codes
- mods/modusocket: init vars to 0 to silence compiler warnings
- remove socket.timeout class, use OSError(ETIMEDOUT) instead
- moduos: remove uos.sep, as it's strictly optional
- mptask: allocate flash VFS struct on the heap to trace root ptrs
- mods/modutime: use generic sleep_ms and sleep_us implementations
- update to use size_t for tuple/list accessors
- update for changes to mp_obj_str_get_data
- mods/pybi2c: raise OSError if readfrom_mem fails to write addr
- modmachine: return frequency value directly, like other ports
- pybuart: make parity specifications consistent with HW API
- mods/pybi2c: make machine.I2C constructor/init conform to HW API
- mods/pybi2c: make readfnom_mem_into/writeto_mem return None
- mods/pybpin: remove toggle() method

teensy port:
- convert to use builtin help function
- main: remove unnecessary header includes
- lexerfrozen: make mp_lexer_new_from_file raise an exception

esp8266 port:
- convert to use builtin help function
- factor out common linker code to esp8266_common.ld
- switch to use OO version of FatFs library
- change to use new generic VFS sub-system
- fatfs_port: include new oofatfs header
- machine_pin: implement pin ioctl protocol
- modmachine: add Signal class
- mpconfigport.h: remove obsolete MICROPY_FATFS_VOLUMES config
- uart: add support for polling uart device
- moduos: populate release field of uname in case it was GC'd
- mpconfigport.h: enable help('modules') feature
- update lexer constructors so they can raise exceptions
- only execute main.py if in friendly REPL mode
- enable micropython.schedule() with locking in pin callback
- change machine.Timer callback to soft callback
- machine_pin: add "hard" parameter to pin.irq, soft by default
- machine_pin: make pin.irq arguments positional
- machine_pin: fix memset size for zeroing of pin_irq_is_hard
- machine_pin: fix pin.irq() to work when all args are keywords
- modesp: use mp_obj_str_get_str instead of mp_obj_str_get_data
- modesp: remove long-obsolete and unused espconn bindings
- update to use size_t for tuple/list accessors
- update for changes to mp_obj_str_get_data
- remove unused entry in port root pointers
- README: replace reference of alpha status to beta status
- README: add notice about 512K version
- change default settings to mount flash at root dir
- esp8266.ld, esp8266_ota.ld: grow main firmware size by 32KB
- modesp: flash_user_start: Use value from linker script
- modules/flashbdev: reserve one sector for native code storage
- scripts: move drivers/modules to modules/ (frozen bytecode)
- scripts: move initsetup & port_diag tools to modules/
- ets_alt_task.c: prevent spurious large increment of ticks_ms()
- modnetwork: in connect, fix potential buffer overflows
- machine_uart: add uart.any() method
- modules: mount filesystem at root when creating for first time
- mpconfigport.h: remove duplicate link to lwip module
- rename machine.Pin high/low methods to on/off
- add ilistdir in uos module

zephyr port:
- help: update n_args param type to size_t
- remove deprecated .mdef file
- add separate Zephyr config for "minimal" build
- enable SLIP networking for the default build
- convert to use builtin help function
- make sure that correct Zephyr config is used for "minimal" build
- allow to have per-board Zephyr config fragments
- prj_frdm_k64f.conf: add, enable Ethernet support
- Makefile.zephyr: support and default to networked (SLIP) QEMU
- README: describe many gotchas of networked builds
- enable IPv6 networking in addition to IPv4
- add qemu_cortex_m3 config fragment
- main: don't unconditionally dump stats on each GC
- README: network startup issues with frdm_k64f resolved
- modzephyr: add a module for Zephyr-specific things
- modzephyr: fix typo in identifier
- make sure that generated prj.conf is updated only on content changes
- move "minimal" configuration building to a separate wrapper script
- main: nlr_jump_fail: Fix noreturn warning
- main: remove unused __fatal_error()
- main: move lexer constructor to within NLR handler block
- zephyr_getchar: use native k_sem instead of legacy nano_sem
- prj_base.conf: disable legacy kernel compatibility
- prj_base.conf: enable TCP (and UDP explicitly)
- Makefile: rework to use modern, official build integration
- Makefile: add workaround (fix?) for broken builds for DTS targets
- fix NLR segfault in minimal build
- modusocket: initial version of usocket module for Zephyr
- integrate modusocket into build
- modusocket: implement bind() and connect()
- modusocket: implement send()
- modusocket: implement recv() for UDP sockets
- modusocket: implement recv() for TCP sockets
- prj_base.conf: add config for net_buf logging
- modusocket: be sure to use MP_OBJ_FROM_PTR
- modusocket: factor out socket_new() function
- zephyr_getchar: explicitly yield to other threads on char availability
- Makefile: add "test" target, runs testsuite in QEMU
- modusocket: factor out "extended k_fifo API"
- modusocket: implement listen()
- modusocket: socket_bind: Don't set recv callback on STREAM sockets
- modusocket: implement accept()
- mpconfigport.h: fix build if usocket module is disabled
- modmachine: add Signal class
- machine_pin: implement pin protocol for machine.Signal support
- modusocket: call net_nbuf_print_frags() in recv callback if DEBUG > 1
- modusocket: strip packet header right in the receive callback
- modmachine: implement machine.reset()
- main: configure IPv4 netmask and gateway to allow Internet access
- add 96b_carbon configuration
- modusocket: refactor send() into stream write() method
- modusocket: enable stream write() method
- modusocket: refactor recv() into stream read() method
- modusocket: add read/readline/readinto stream methods
- modusocket: sock_read: Check socket status only at the start of packet
- modusocket: add dummy makefile() implementation
- Makefile: add debugserver Zephyr target
- mpconfigport.h: enable line number information for scripts
- main: remove superfluous include
- modusocket: add dummy setsockopt() implementation
- modusocket: add SOL_SOCKET and SO_REUSEADDR constants
- prj_qemu_x86.conf: bump RAM size to 320K
- README: update to require Zephyr 1.8
- modusocket: wrap pkt_get_info() call
- modusocket: update for net_pkt refactor
- modusocket: switch to net_pkt_append() returning length
- modusocket: if there're no packets in recv_q, cancel waiter
- modusocket: implement getaddrinfo()
- modusocket: first step to switch to alternative FIFO processing
- modusocket: get rid of cur_pkt object member
- main: check default netif before applying operations to it
- modusocket: getaddrinfo: Use RAISE_ERRNO for proper error decoding
- modusocket: getaddrinfo: Raise OSError on resolution timeout, etc
- modusocket: use DEBUG_PRINT macro name as other modules do
- rename machine.Pin high/low methods to on/off
- don't send more than MTU allows
- modusocket: handle a case when recv_q is empty when EOF is signaled

pic16bit port:
- main: make nlr_jump_fail never return
- main: make mp_lexer_new_from_file raise an exception

README:
- explicitly mention "await" support, and formatting for keywords
- add link to docs.micropython.org
- describe extmod/ dir
- change Travis & Coveralls badges to not use link references

travis:
- unconditionally run coveralls analysis, even if others failed
- change an stmhal rule to build PYBV11 instead of default PYBV10

gitattributes:
- add .mpy files to list of binary files
- remove obsolete lines

docs:
- fix some minor spelling mistakes
- add documentation for lcd160cr module
- pyboard/tutorial: add tutorial for LCD160CR
- library/lcd160cr: fix set_brightness range, should be 0..31
- machine.Timer: move WiPy adhoc parts to its documentation
- machine: add explicit note on machine module level and scope
- usocket: clarify exceptions used
- usocket: elaborate "Constants" section
- usocket: clarify description of various methods
- usocket: dedent Methods section
- uio: describe differences between uPy an CPy stream hierarchy
- conf.py: add myself as a copyright holder on the docs
- uio: typo fixes/lexical improvements
- pyboard/tutorial/lcd160cr_skin: fix typo, get_touched->get_touch
- for LCD160CR driver and tutorial, add link to positioning image
- esp8266/tutorial: specify the baudrate in picocom example command
- add M-logo as favicon
- library/pyb.Pin: minor typo fix, B6 should be A0
- library/machine: make separate TOC for WiPy vs non-WiPy
- uos: remove mention of uos.sep
- library/lcd160cr: mention the valid values for set_power() method
- modify Makefile and indexes to generate cPy-differences pages
- uhashlib: provide port-neutral description
- Makefile: define and use PYTHON as the interpreter for CPYDIFF
- machine: fix formatting of Constants section
- library/lcd160cr: add note about supported JPEG format/encodings
- library: add framebuf documentation
- library/lcd160cr: add link to framebuf page
- esp8266/tutorial: update since esptool 1.3 added Python 3 support
- library/framebuf: fix typo in bit-width for MVLSB description
- library/machine.I2C: fix scan() doc to match implementation
- library/btree: add btree module docs
- utime: de-conditionalize description of sleep_ms() and friends
- uos: de-conditionalize statvfs() description
- machine.SPI: remove outdated wipy chunk
- machine.Pin: move wipy-specific details to its own docs
- machine.Pin: move wipy-specific methods to its docs
- esp8266/general: start explicit "Known Issues", mentioned RTC inaccuracy
- library/builtins: int: Add notice on byteorder param for to/from_bytes
- library/machine.UART: remove some conditionals
- utime: deconditionalize description of sleep()
- usocket: deconditionalize
- uhashlib: deconditionalize
- esp8266/tutorial/intro: reword section on flash size requirement
- library/micropython: deconditionalize
- library/uos: urandom: Generalize description
- library/ussl: deconditionalize, wipy notes moved to its documentation
- machine.UART: deconditionalize normal methods
- machine: move machine.main() misnomer to wipy's known issues
- library/machine: typo fix in machine_callbacks section
- library/machine.UART: remove pyboard-specific section
- wipy/quickref: update reference for change to I2C API
- wipy/general: add section about specifics of I2C implementation
- library/machine.I2C: deconditionalise all methods
- library/machine.*: add cross-reference label to individual classes
- esp8266/quickref: add links from quickref page to machine classes
- library/machine.I2C: remove WiPy-specific return values
- library/machine.SPI: fix formatting of bullet list to stop warning
- library/uos: add description of uos.ilistdir() function
- machine.Pin: there's no toggle() method in MicroPython hardware API
- machine.Signal: add initial draft description of Signal class
- library/index: add important summary of the intro section as warning
- change single occurrence of "Micropython" to "MicroPython"
- library/micropython: document the newer micropython functions
- library/machine.UART: update and improve uart.any() docs
- library/machine.Pin: remove .id() method and .board class attr

examples:
- hwapi: use Signal for inverted LED on ESP-12
- hwapi: consistently use Signal class to define LEDs
- button_reaction: update for time_pulse_us() no longer raising exc
- hwapi: add hwconfig_pyboard.py for pyboard
- hwapi: be sure to import Signal when it's used
- hwapi/soft_pwm: use Signal on()/off() methods
- embedding/README: convert to markdown, grammar and clarity fixes
- embedding: place lexer constructor within NLR handler block
- hwapi: add config for Zephyr port of 96Boards Carbon
- hwapi/hwconfig*: use inline Signal() args where possible
- hwapi/soft_pwm2_uasyncio: update for call_later_ms()