Add -DNDEBUG to AM_CPPFLAGS.

libOggFLAC has been deprecated for 5 years now, and we havn't been
testing it for a long time.  Let's delete it.

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

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.

Auto-enable the plugin when OpenSSL was found.

To demonstrate the new I/O thread.  libsoup is well-integrated into
the GLib main loop, which made this plugin pretty easy to write.

As a side effect, we have to initialize the I/O thread in all debug
programs that use the input API.

Was always displayed as "no", even if one was found.

All modern distros ship 0.5, so there's no need to support old and buggy
ffmpeg versions.

Otherwise OGGs can't be played.

This makes FreeBSD detect libogg correctly. The '==' operator is an
undocumented GNU extension to test(1) and cannot be relied upon to
exist and do the right thing. POSIX mandates string comparisons to be
done using "test foo = bar".

The client-to-client protocol was added, and that justifies increasing
the protocol version.

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

When the configure options were moved around for 0.16, the order was
changed, and the Tremor check broke.

A bit of automake magic (see info automake "Per-Object Flags").
Compile-tested.

Use "printf" instead.

Don't create a modified copy for out-of-tree builds.

It is known to crash instantly.

Add new config parameter 'device' to audio_output type "osx":
- if not supplied or set to "default", open default device
- if set to "system", open system device
- otherwise 'device' should be an audio device name: mpd will find and
  open the specified audio device, falling back to the default
  device if it's not found