This patch generalizes the concept used in Piano to wake up the event loop
so it can react to something happening on a secondary thread.
Basically, there's a pipe who is always part of the file descriptor set we
pass to select(), and calling wake() simply writes a little to that pipe.
* Add a LibAudio, and move WAV file parsing there (via AWavFile and AWavLoader)
* Add CLocalSocket, and CSocket::connect() variant for local address types.
We make some small use of this in WindowServer (as that's where we
modelled it from), but don't get too invasive as this PR is already
quite large, and the WS I/O is a bit carefully done
* Add an AClientConnection which will eventually be used to talk to
AudioServer (and make use of it in Piano, though right now it really
doesn't do anything except connect, using our new CLocalSocket...)
Don't process any more events. We already prepend the remaining events in
this loop to the outer loop if needed.
If there were any more events queued after the exit request, the iteration
code would make an invalid access into 'queued_events'.
Fixes#300.
