Provide an API for submitting additional tags from the stream.

Avoid while(true) loops, and convert them to a loop with a proper
condition.

Since the aac and mod plugins have told MPD that they cannot seek, MPD
will never send a SEEK command to them.  Removed the SEEK comand
checks from both plugins.

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.

Each music chunk can now carry a tag object.  Decoder plugins which
support it (e.g. oggvorbis) may use this to inject decoded tags into
their output.

These two functions will care about memory allocation and deallocation
in the future.

Add doxygen compatible comments.

The "volatile" keyword doesn't help here, because we have proper
memory barriers, but it disables some optimizations.  Remove it.

The name "num_chunks" expresses the meaning of the variable better.

Rename all variables and struct members.

Don't bother to pass these values as parameters to tail_chunk().

Last music_pipe rename patch: renamed the global variable (singleton).

Replace all direct music_pipe struct accesses with wrapper functions.
The compiled machine code is the same, but this way, we can change
struct internals more easily.

Eliminate the deprecated utils.h memory allocation functions.

.. and rename dc.audioFormat to dc.in_audio_format.  The music pipe
does not need to know the audio format, and its former "audioFormat"
property indicated the format of the most recently added chunk, which
might be confusing when you are reading the oldest chunks.

Don't make tail_chunk() calculate the frame size again.

Rename all functions to the new prefix.

.. and rename ob_chunk to struct music_chunk.

No CamelCase in the file name.  The output_buffer struct is going to
be renamed to music_pipe.  There are so many buffer levels in MPD, and
calling this one "output buffer" is wrong, because it's not the last
buffer before the music reaches the output devices.

Commit 1a4a3e1f moved decoders into a static array, but failed to
enable those plugins who did not have an init() method at all.
This patch corrects the "enabled" check.

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.

Currently, there is no way to dynamically load decoder plugins, thus
we don't need a dynamic list to manage them.

The decoder_plugin structs must never change.  Don't work with
non-const pointers.

Eliminating the deprecated linked list library.

Don't use the deprecated functions from utils.h.

Eliminate code already provided by GLib.

Return NULL instead of the input value if there is nothing to fix.
This way, the caller doesn't have to use the xfree() hack.

Make the pointers "device" and "name" non-const, so we don't need the
xfree() hack.  The default value is expressed as NULL.

We don't need to sanitize the path, because the mapper already checks
for malformed paths.

Make map_directory_child_fs() refuse the names "." and "..".  This is
currently the interface where an attacker may inject a manipulated
path (through the "update" command).

Nearly all mapper functions can fail and will then return NULL.  Add
checks to all callers.

Added the function map_spl_utf8_to_fs() which replaces
utf8_to_fs_playlist_path().

g_error() is fatal by default.  Use g_warning() for non-fatal
initialization errors.

http://xkcd.com/292/

If nobody sent a command, the player isn't waiting for the decoder.
Don't wake it up.

The player should always be woken up when the decoder quits.

Eliminate one goto in decodeStart() by moving some cleanup to
decoder_task().

switch looks much nicer than if/elseif/... and gcc generates nice
warnings when a new command is added to the enum.