This plugin is horrible code, I mean it.  Last year, I tried hard to
fix it, but I figured would take less time to do a full rewrite.
Given that I don't even have any device that supports RAOP, I can't do
that properly.  After 16 months, nobody volunteered for fixing it.
Hereby, I delete it, because having no RAOP plugin is better than
having this mess.  Sorry.

Use libasound's polling functions, implement a bridge to GSource /
GPollFD and send idle events to clients when an external program
changes the ALSA mixer volume.

Better error handling.

Provide _lock() and _unlock() to wrap all accesses from the mixer
plugin.

Use these instead of exposing the internal roar_t struct.

Should fix build errors for Win32.

Remove trailing whitespace found by this command:
find -name '*.[ch]' | xargs grep "[[:space:]]$"

Remote Audio Output Protocol (RAOP), for Apple devices.

After we've been hit by Large File Support problems several times in
the past week (which only occur on 32 bit platforms, which I don't
have), this is yet another attempt to fix the issue.

Add a "mode" argument to open_cloexec() instead.

Added the "fd_util" library, which attempts to use the new thread-safe
Linux system calls pipe2(), accept4() and the options O_CLOEXEC,
SOCK_CLOEXEC.  Without these, it falls back to FD_CLOEXEC, which is
not thread safe.

This is particularly important for the "pipe" output plugin (and
others, such as JACK/PulseAudio), because we were heavily leaking file
descriptors to child processes.

Don't let the mixer plugin "override" the libpulse callbacks.
Instead, add a "mixer" attribute to the pulse_output struct, and call
the mixer on all interesting events.

It's possible to have a mixer implementation which does not explicitly
need the methods open() and close().

Moved the check from pulse_mixer_open() to pulse_mixer_update().

This is a complete rewrite of the PulseAudio output plugin.  It uses
the asynchronous API, which gives us more control over everything.
Additionally, it connects to the PulseAudio server on startup, and
keeps this connection up while MPD runs.  During pause, instead of
closing the stream, it enables "cork".

This allows the mixer object to access its associated audio output
object.

This mixer plugin may be used instead of the traditional global
software mixer.  It integrates with the "volume" filter plugin, and
can control the software volume of an audio output which has no
hardware mixer.

strcasecmp() is locale dependent, making it a bad choice for internal
string comparisons.

This allows you to select controls with duplicate names.

Using two different kinds of locks may result in a race condition with
a deadlock.  The libpulse callbacks need no locks at all, because the
mainloop object can be assumed to be already locked.

snd_config_update_free_global() frees cached ALSA configuration.  This
keeps valgrind a little bit more quiet.  This patch moves the call
from the open() method into the finish() method, which seems more
natural: it allows the use of the config cache, and improves the
cleanup phase.

Added an assertion in mixer_set_volume().  Removed the range checks
from the ALSA and OSS plugins.