lbcdclient unpacks with a version 3 template and fails to unpack a
version 2 packet because there's not enough data. With this change
slbcd packs using a version 3 template, so the packet is long enough
for lbcdclient.

Clarify site-specific changes
Add PowerDNS requirements

Original log message:

> Author: Russ Allbery <rra@stanford.edu>
> Date:   Mon Jul 18 13:16:32 2011 -0700
>
>     Change socket send errors into a warning in the poller
>
>     The poller would die if sending a packet to a remote host returned
>     an error, but the kernel may return an error if the remote host is
>     known to be down.  If we just ignore the error and then never get
>     a reply from the remote host, we'll conclude that it was down, which
>     is the correct behavior.  Turn this die into a warn so that the
>     poller doesn't exit.
>
>     Change reported by Bill MacAllister.