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

The standard has been renamed since the early draft that was
implemented in MPD.

For type safety and code readability.

Reduce header dependencies.

Generate more detailed error messages.

Eliminate duplicate definition (in input plugin and decoder plugin).

This plugin uses the MP4v2 library to play mp4/m4a files.
It is limited to file_decode.

The new class is pluggable, to prepare for gzipped database files.

For now, the TextFile class remains, and will be refactored away
later.

libfs.a depends on libsystem.a.

Eliminate duplicate code.

It happened to me when doing the Haiku port, src/mpd failed to
be relinked properly when editing source files, and likely also
happens on win32, although I didn't try this change.

When building for windows, src_mpd_DEPENDENCIES is overriden.

Automake then disables the default version which contains all
the static libraries. In Makefile.in:
@HAVE_WINDOWS_FALSE@src_mpd_DEPENDENCIES = libmpd.a \

Instead we use EXTRA_src_mpd_DEPENDENCIES which is meant for this.

Fixes breakage by commit 1a619522

Invoke "ant" when a Java source is modified.

Missing piece from commit e0ca4347

Implement a "bulk" edit mode that postpones both UpdateQueuedSong()
and OnModified().  This way, the playlist version gets incremented
only once.  More importantly: when adding multiple songs to a queue
that consists of only one song, the first song that got added will
always be played next.  By postponing this choice, all newly added
songs get a chance to become the next song.  Fixes the second (and
last) part of Mantis ticket 0004005.