Necessary for "final" on gcc 4.6.

Use a listener interface instead of GlobalEvents.

There was quite a lot of duplicate code for loading DetachedSong
objects, with different semantics for "securely" loading local files.

Don't use global variable.

Another big chunk of code for multi-player support.

From now on, struct Song will be used by the database only, and
DetachedSong will be used by everybody else.  DetachedSong is easier
to use, but Song has lower overhead.

Finally restores an important feature that has been broken for several
months when the PlayerThread started working with Song copies instead
of pointers to the Queue's Song instances (commit e96779de).

Move code from class Instance.

More preparations for multi-player support.

This is the beginning of multi-player support.  There will be support
for multiple Partition objects in one MPD process.

Parses CUE data from the "CUESHEET" tag.  Needs further integration in
the update thread.

Pass a callback table to scan_file() and scan_stream(), instead of
returning a tag object.

Based on the APE reader.

Don't call g_error(), which will abort the process and dump core.

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.

Renamed functions.

This is a rather huge patch, which unfortunately cannot be splitted.

Instead of using our custom ioops.h library, convert everything to use
the GLib main loop.