Code simplification.

Reduce heap usage by reducing the number of malloc() / free() calls.

D'oh, we were reading 16 bit integers instead of 32 bit integers!
That caused silence when trying to play a 32 bit input file on a 24
bit sound card (e.g. USB sound chips with 24 bit packed samples).

.. and a minor tweak for libFLAC+libogg detection.

Eliminate an unnecessary source of deadlocks.

The pkg-config file was added by the Debian package maintainers, and
unfortunately, the rest of the world doesn't have it.

Add M4 function MPD_AUTO_PKG_LIB for pkg-config with AC_CHECK_LIB
fallback.

Don't abort the configure script when avahi could not be
auto-detected.  It previously did, because there was no custom "fail"
action for PKG_CHECK_MODULES.

Don't add those to MPD_CFLAGS / MPD_LIBS.

Better name, better documentation.

The output thread could hang indefinitely after finishing CANCEL,
because it could have missed the signal while the output was not
unlocked in ao_command_finished().

This patch removes the wait() call after CANCEL, and adds the flag
"allow_play" instead.  While this flag is set, playback is skipped.
With this flag, there will not be any excess wait() call after the
pipe has been cleared.

This patch fixes a bug that causes mpd to discontinue playback after
seeking, due to the race condition described above.

Fixes assertion failure when a stream callback is invoked too late
after a format change.

Merge common code.

Eliminate duplicate code.

Checkbashisms (part of the Debian devscripts) pionted this out.

Be sure to stop the operation at some point when the server isn't
responding.

Check if the stream is suspended; wake up the main loop when it
becomes suspended.

Not a bool.

Unlock the mainloop in all code paths.

This warning should only be logged when we really received something.
When the client disconnects, G_IO_IN is triggered, and the read
returns G_IO_STATUS_EOF.

Move the variable "vbr_update_acc" into the #ifdef block.

In the "vorbis" plugin, this is a copy of the old flush() method,
while flush() gets a lot of code remove, it just sets the "flush" flag
and nothing else.  It doesn't start a new stream now, which should fix
a few problems in some players.

Enable gcc optimizations.

The method may take longer, and we shouldn't be holding the lock.

It used to ignore the decoder_data() return value.

libwavpack provides int32_t samples, and wants uin32_t for sample
counts.