Playlist file name first, to be consistent with the other functions in
this library.

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.

Replaces GLib's GError.

.. instead of rolling own classes.

The "bool" type is built-in.

Improve error reporting and handling.  command.c gets the new function
print_error(), which sends a GError to the client.

Reduce header dependencies.

These fixes were mostly generated with `codespell' [0] and manually
reviewed.

[0] http://git.profusion.mobi/cgit.cgi/lucas/codespell/

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.

Don't declare and export variables specific to stored playlists in
playlist.c/playlist.h.

On some systems, the time_t data type was not present, because
stored_playlist.h didn't include the time.h header directly.

The function deletePlaylist() shouldn't be in playlist.c.

Don't use our deprecated linked list library, use GLib's GPtrArray
instead.

Pass index arguments as unsigned integers.  They must not be negative,
and even if some caller accidently passes -1, it won't pass the bound
checks (since it's now 2**32-1).

spl_list() provides an interface for enumerating all stored playlists.
This separates the internal playlist logic from the protocol specific
function lsPlaylists().

The return value of spl_append_uri() was somewhat buggy: some branches
returned ACK_* values, and some an enum playlist_result.  Unify this.

Rename addToStoredPlaylist() to spl_append_uri(), and remove the
clearStoredPlaylist() macro.

The two functions clearStoredPlaylist() and addToStoredPlaylist()
don't belong into playlist.c.  clearStoredPlaylist() was a wrapper for
spl_clear(), and is converted into a CPP macro for now.

Renamed all public functions, prefix is "spl_".

No CamelCase in file names.

Again, a data type which can be forward-declared.

Return an "enum playlist_result" value instead of calling
commandError() in storedPlaylist.c.