The Release Track Id uniquely identifies a recording on a release - that
is, even if a recording appears twice on a release (meaning that the
combination of recording and release id are not enough to figure out
which one it is), the release track id will allow differentiating the two.

The tag names are taken from
https://musicbrainz.org/doc/MusicBrainz_Picard/Tags/Mapping

There's always the "PCM" decoder plugin, which was never checked by
configure.ac.

MPD can easily be used as a database provider for the proxy database
plugin.  In that case, it needs only one "null" output, and no real
output plugin.

Allow building a smaller MPD binary for people who don't need DSD.

The name "cue" was listed twice in "mpd --version".

EXIT_SUCCESS and EXIT_FAILURE are defined in stdlib.h, not unistd.h.
D'oh!

Move code from the Vorbis and FLAC decoder plugins.

Eliminates the functions _new() and _free().