seq: remove-filter: rewrite as GObject-derived object
In UAPI of ALSA Sequencer, 'struct snd_seq_remove_events' has reserved
member for future use. In the case, the convention of this project lets
us to use class instead of structure.
Additionally, current implementation of ALSASeq.RemoveFilter doesn't
support multiple condition to query events for removal. It's not
necessarily convenient.
git://git.alsa-project.org / alsa-gobject.git / commit