Replaces GLib's GError.

Let the database plugin do the match.

Reduce the number of lock/unlock cycles, and make database handling
safer.

Wrap songvec_find() and other songvec methods.

Random access is not needed, and a linked list is easier to manage: we
don't need to (re-)allocate the pointer array.

Pass only the "name" to a directory, instead of the full (relative)
path.

"stat" is a macro on mingw32, which is a pretty stupid thing, and this
commit works around this build failure.

Use this struct for db_walk().

Keep those when scanning for empty directories.  The check in
playlist_vector_is_empty() was missing.

Cast the constant to dev_t, not to unsigned.

Fix gcc warning.

Don't open the music directory for each "lsinfo" call.  Get the list
of playlist files from the memory database.

After we've been hit by Large File Support problems several times in
the past week (which only occur on 32 bit platforms, which I don't
have), this is yet another attempt to fix the issue.

*sigh* another Large File breakage.  ino_t/dev_t this time.  We need
to include config.h in directory.h to get this straight.

Moved code from db_get_song().

Renamed directory_get_directory() to directory_lookup_directory().
Added API documentation.

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.

[mk: fixed whitespace errors; use delete_song() instead of
songvec_delete()]