Obsolete class CloseSongEnumerator, which was a kludge.

Let the caller decide whether to strip.  Only remove \n and \r
(end-of-line markers).

Revert to the old API before commit e9e55b08, removing unnecessary
bloat.

Automate the life cycle, making the code safer.

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 g_str_has_prefix().

Overload the name.

Replaces struct playlist_provider.

Replace g_strchug() calls with a cheaper implementation.