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

Don't allocate each replay_gain_info object on the heap.  Those
objects who held a pointer now store a full replay_gain_info object.
This reduces the number of allocations and heap fragmentation.

Make it X_decoder_plugin.c.

This function replaces the replay_gain_info parameter for
decoder_data().  This allows the decoder to announce replay gain
changes, instead of having to pass the same object over and over.

This patch changes the following decoder plugins to implement
stream_tag() instead of tag_dup():

 faad, ffmpeg, mad, modplug, mp4ff, mpcdec, oggflac

This simplifies their code, because they do not need to take care of
opening/closing the stream.

Remove the data_time parameter from decoder_data().  This patch
eliminates the timestamp counting in most decoder plugins, because the
MPD core will do it automatically by default.

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.

This fixes a regression due to a typo caused by "decoder: use
audio_format_init_checked()".

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

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.

It makes no difference right now, but we're about to add an endianness
flag and will want to make sure it's correctly initialised every time.

The "mpcdec" plugin is based on the libmpcdec library.

Renamed variables and functions.

This updates the copyright header to all be the same, which is
pretty much an update of where to mail request for a copy of the GPL
and the years of the MPD project. This also puts all committers under
'The Music Player Project' umbrella. These entries should go
individually in the AUTHORS file, for consistancy.

Fixed the log domains of the renamed decoders.  Added G_LOG_DOMAIN
macros in decoders which don't have one already.

This plugin is based on "libmpcdec".

Some plugins used the APE or ID3 tag loader as a fallback when their
own methods of loading tags did not work.  Move this code out of all
decoder plugins, into song_file_update().

SEEK_SET is defined by unistd.h.  Explicitly include it.

Refuse to play audio formats which are not supported by MPD.

According to the documentation, mpc_decoder_decode() returns an
mpc_uint32_t.  Since the special return value (mpc_uint32_t)-1
translates to a very large long integer, this may cause segmentation
faults if not interpreted properly.

Don't hard-code the factor "2".

Removed 3 superfluous decoder_get_command() invocations.

mpc_to_mpd_buffer() converts a whole chunk at a time.  This eliminates
3 local variables in mpc_decode().

Don't split the buffer conversion loop.  When libmpcdec returns a
chunk, convert and send the whole chunk at a time.  This moves several
checks out of the loop, and greatly improves performance.

Don't use deprecated MPD libraries.

The buffer is always casted to int32_t* anyway; declare it as int32_t
array, and remove the cast.

Since each "eof=true" is followed by "break", the variable is
superfluous.

The stream_decode() and file_decode() methods returned a boolean,
indicating whether they were able to decode the song.  This is
redundant, since we already know that: if decoder_initialized() has
been called (and dc.state==DECODE), the plugin succeeded.  Change both
methods to return void.

Having an array instead of individual variables allows the use of the
replay_gain_mode enum as an array index.

Renamed functions and variables.

Instead of checking the stream_types bit set, we can simply check
whether the methods stream_decode() and file_decode() are implemented.

Don't pass the "seekable" flag with every decoder_data() invocation.
Since that flag won't change within the file, it is enough to pass it
to decoder_initialized() once per file.

The strings were constant, but the pointers weren't.  C syntax is
somewhat tricky..

All decoder_plugin structs are initialized at compile time, and must
never change.