Don't limit the "rewind" input plugin to CURL streams.

Make it X_decoder_plugin.c.

The replay_gain_state struct holds the precalculated scale factor,
which is removed from struct replay_gain_info.

Don't add these to the global MPD_CFLAGS and MPD_LIBS.  This allows
test programs to link without libopenal.

This replaces the rewinding buffer code from the CURL input plugin.
It is more generic, and allows rewinding even when the server sends
Icy-Metadata (which would have been too difficult to implement within
the CURL plugin).

This is a rather complex patch for the stable branch (v0.15.x), but it
fixes a serious problem: the "vorbis" decoder plugin was unable to
play streams with Icy-Metadata, because it couldn't rewind the stream
after detecting the codec (Vorbis vs. FLAC).

Use the plugin instead of the glue code in normalize.c.  This is used
wrapped inside a "autoconv" filter, to enable normalization for all
input file formats.

This plugin is the groundwork for MPD's future generic CUE sheet
support.  That's not complete yet, e.g. there is no way for a playlist
plugin to address an arbitrary position within a music file.

Make archive_file a "real" struct, extended by all plugins.  Add the
plugin pointer to it.  Wrap all method calls in functions.

Moved the archive plugin "extern" declarations into each plugin
header.

Based on libiso9660.

For the fluidsynth plugin.

This plugin is based on libzzip.

This fixes "make distcheck".

Wrap the AudioCompress library in a filter plugin.

This patch prepares support for floating point samples (and probably
other formats).  It changes the meaning of the "bits" attribute from a
bit count to a symbolic value.

Copied sources from
http://beesbuzz.biz/code/audiocompress/AudioCompress-2.0.tar.gz

[mk: created this patch under fluffy's name and fixed some gcc
signed/unsigned comparison warnings]

Unified function for converting an audio_format object to a string,
for log messages and for the "status" command.

Let the audio_check library verify the audio format in all (relevant,
i.e. non-hardcoded) plugins.

These functions are a wrapper for audio_valid_X().  On error, they
return a GError object.

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.

When using wave encoder with httpd audio output mpd can input this stream via http and audiofile decoder.
This for example opens simple way to configure lossless audio streaming port(like jack or pulseaudio does but without overhead).
Another possibility can be using it for gathering raw data for visualization plugins (If sync issue will be resolved)

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.