Don't initialize "vc" and "cs" with FLAC__metadata_object_new(); that
value is overwritten by FLAC__metadata_get_tags() and
FLAC__metadata_get_cuesheet().

External cue sheet file for "file.flac" should be named as "file.flac.cue".

Initialize flac_data.tag right after flac_data_init().  This way, the
"goto fail" won't jump to the point where tag_free(NULL) can be
called.

Move the declaration of "i" into the "for" loop.

Cuesheets are often saved as vorbis comment
flac files (CUESHEET=.. case doesn't matter).
We can parse this now and use the information to
tag the subtracks (from the embedded cuesheets).

Previous cast to float didn't have any effect because one value is uint
and the other is a floating type but the number itself is even..
This caused some tracks to end before they were really at an end.

The cue sheet embedded in a flac file doen't contain any information
about track titles and similar.  There are three possibilities: Use an
external cue sheet that includes these information, use a tag CUESHEET
with a cue sheet including these information or use tags.  I think the
latter is the best option and is already used by other projects.

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.

So far only seekpoints are supported, so no proper tagging yet
except for track number and track length.
Tagging should be done by parsing the cue sheet which
is often embedded as vorbis comment in flac files.
Furthermore the pathname should be configurable like "%A - %t - %T",
where %A means Artist, %t track number and %T Title or so.

After the decoder command was obtained, don't wait until libflac
detects EOF (as a side effect), quit the decoder immediately.  This
check was missing completely.

When the MPD core sends the decoder a command while
flac_process_single() is executed, this function fails.  Abort the
decoder only if not seeking.  This fixes a seeking bug.

Parse the vorbis comments in libflac's metadata_callback and pass them
as tag struct to the decoder API.

Preparing for per-plugin configuration sections in mpd.conf.

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().

Free the tag object when it turns out to be empty.  This simplifies
several functions and APIs.

Use tag_is_empty() instead.

Renamed types, functions, variables.

Use GLib's G_GNUC_UNUSED instead of gcc.h's mpd_unused.

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

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

Define the special value "-1" as "unknown size".  Previously, there
was no indicator for streams with unknown size, which might confuse
some decoders.

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.

Renamed functions and variables.

Instead of having a seprate try_decode() method, let the
stream_decode() and file_decode() methods decide whether they are able
to decode the song.

The flac plugin wasn't initialized properly when an OGG file was being
decoded.  For some reason, flac_process_metadata() was explicitly not
called for OGG files.  Since that seems to fix the issue, make it
always call flac_process_metadata().

Since decoder_list.c does not include the libflac headers, it cannot
know whether to add the oggflac plugin to the decoder list.  Solve
this by always enabling the oggflac sub-plugin, even with older
libflac versions.  When the libflac API cannot support oggflac,
disable the plugin at runtime by returning "false" from its init()
method.

Disable flac's "oggflac" sub-plugin when libflac does not support
ogg-flac files.

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.

Don't return 0/-1 on success/error, but true/false.  Instead of int,
use bool for storing flags.

Call ob_clear() in decoder_command_finished() instead of implementing
that call in every decoder plugin.