Changed "0" to "NULL".

At the last line of handle_addid(), the playlist_result value has
already been evaluated.  Don't return this variable, it's the wrong
type.

addToPlaylist() has a "enum playlist_result" return value.  Convert
that to "enum command_return" properly.

On failure, the function should return NULL, not a boolean.

sparse cannot deal with C++.

sparse complains that a lot of limit.h macros are missing.  Define
them to keep sparse quiet.

Turn the "return false" error handlers into "return NULL".

Moved the hash table initialization from sticker_list_values() to the
new function sticker_new().  This fixes a memory leak in
sticker_list_values().

sticker_list_values() is only used internally in sticker.c.  Remove
sticker_song_list_values() completely, it is superseded by
sticker_song_get().

The sticker struct can be used for enumerating values.  This will
replace the sticker_list_values() function.

Don't dump the volume of all mixers.

In some rare cases, there was a race condition between the output
thread and the main thread: when you disable/enable an output device
in the main thread, this caused a crash in the output thread.  Protect
the whole mixer struct with a GMutex to prevent that.

This patch allows the output plugins to import only mixer_list.h,
instead of the full mixer_api.h (which would expose internal
structures).

mixer_control.h should provide the functions needed to manipulate a
mixer, without exposing the internal mixer API (which is provided by
mixer_api.h).

Return true/false on success/failure, instead of 0/-1.  Pass
true/false instead of 1/0 for the "rel" boolean parameter.

Check for NULL not necessary here

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.

When the destination chunk was empty in cross_fade_apply(), it had no
audio_format attached (an attribute which is only used for assertion
in the debug build).  cross_fade_apply() should assign it the
audio_format of the second chunk (if available), otherwise MPD will
crash.

When there are chunks which are not yet finished,
audio_output_all_check() returned the size of its music pipe minus
one.  I can't remember exactly why I subtracted 1 from the return
value, it must have had something to do with a former meaning of this
function.  Now it induces assertion failures.

That linker flag got lost when AM_LDFLAGS was removed.

When an audio output device is disabled, also disable its mixer.

No caller must ever pass an invalid device number to
mixer_control_setvol() or mixer_control_getvol().

Very small start..

Passing libraries through LDFLAGS is a mistake that causes link to fail
when using --as-needed. Since the ld arguments are positional, so are
libtool's. Use the proper variable, thus, to pass the libraries.

Replaced both player_stop_decoder() invocations with player_dc_stop(),
which also cleans up the pipe.

In the "CANCEL" command handler, the decoder is stopped twice: first
by player_dc_stop(), then by dc_stop().  Remove the latter.

This function was part of a workaround which we don't need anymore.

After adding the container_scan() method the update_regular_file() method was quite hard to read.
Now there's update_container_file() which deals with container files.
That way normal container files (i.e. without embedded tracks) are handled by the old code like a regular file.
This will fix some of the odd behaviour observed.