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

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.

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.

bzip2-compressed tarballs are obsolete, xz is better and widely
understood.

Fixes regression from commit e96779de.

Move code from class Instance.

Replaces GLib's g_ascii_strcasecmp().

Finally fixes the regression by commit c1f4f1fd.

The new class Path only holds a string pointer without being
responsible for allocation/deallocation.  The FileSystem.hxx library
accepts Path arguments instead of AllocatedPath, to avoid forcing
callers to allocate another string object.