Don't return a writable pointer.

No "force" parameter, pass a default value instead.

Renamed functions, types, variables.

If a song is not within the music directory ("file:///..."), it has no
"parent directory".  The archive code nonetheless dereferences the
parent pointer, causing a segmentation fault.  Check parent!=NULL.

One of the previous patches made MPD consume 100% CPU in a busy wait:
when the music_pipe was full, it did not wait (with notify_wait()) for
free chunks, because a variable has a different meaning now.  Always
pass "true" as the "wait" parameter.

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().

Removed yet another superfluous buffer layer: return the PCM buffer
from pcm_convert() instead of copying PCM data into the
caller-supplied buffer.

The function is unused, since decoder_api() uses music_pipe_write() /
music_pipe_expand() now.

Copy PCM data to the music_pipe_write() buffer, and apply replay gain
/ normalization to it, instead of manipulating the source buffer.

This new API gives the caller a writable buffer to the music pipe
chunk.  This may allow the caller to eliminate several buffer copies,
because it may manipulate the returned buffer, until it calls
music_pipe_expand().

When libvorbis knows that a song is seekable, it seeks around like
crazy in the file before starting to decode it.  This is very
expensive on remote HTTP resources, and delays MPD for 10 or 20
seconds.

This patch disables seeking on remote songs, because the advantages of
quickly playing a song seem to weigh more than the theoretical ability
of seeking for most MPD users.  If users feel this feature is needed,
we will make a configuration option for that.

Decoder plugins must not send partial frames.

Due to rounding errors, it was possible that the fallback resampler
returned partial frames.

getBoolConfigParam() returns an int.  It is not possible to check for
CONF_BOOL_UNSET after it has been assigned to a bool; use a temporary
int value for that.

Older gcc versions complained about shadowed parameters in prototypes.

It returns bool, not int.

When MPD starts without audio output configuration, the "param"
variable is NULL.  This triggers a segmentation fault in both mixer
plugins.

When tremor (libvorbisidec) is used, HAVE_OGGVORBIS was not defined.

This patch allows mpd to recognise the albumartist tag in the way
foobar2000 and others write it to files.

Splitted flac_copy_vorbis_comment() into flac_copy_comment() and
flac_copy_comment().

Simplify flac_copy_vorbis_comment() by moving the comment
identification code out.

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

tag_is_defined() checks whether there is any information in the tag
object.

Use tag_is_empty() instead.

Renamed types, functions, variables.

Calling input_curl_select() after EOF has been reached causes an
assertion failure.  This can happen if the HTTP response is empty.
Check c->eof before calling input_curl_select().

Set the "ready" flag for empty resources.

To check for early connect failures, call curl_multi_info_read() in
the constructor input_curl_open().  This fixes an assertion failure.

Copy changelog items from the upcoming 0.14.1 release.

g_queue_clear() was introduced in GLib 2.14.  Add a macro hack for
older GLib versions to emulate it.

gcc doesn't know that g_error() never returns.  Work around the gcc
warning.

g_get_user_special_dir() was introduced with GLib 2.14.  Don't use it
in older versions.

dest_size is only used in an assertion.  Remove its declaration and
move the formula into the assertion.