ext/wavpack/gstwavpackparse.*: Make wavpackparse also work in push-mode (not seekable...

ext/wavpack/gstwavpackparse.*: Make wavpackparse also work in push-mode (not seekable yet though); some small clean-u...

Original commit message from CVS:
* ext/wavpack/gstwavpackparse.c: (gst_wavpack_parse_class_init),
(gst_wavpack_parse_reset), (gst_wavpack_parse_get_src_query_types),
(gst_wavpack_parse_src_query),
(gst_wavpack_parse_handle_seek_event),
(gst_wavpack_parse_sink_event), (gst_wavpack_parse_init),
(gst_wavpack_parse_create_src_pad),
(gst_wavpack_parse_push_buffer), (gst_wavpack_parse_loop),
(gst_wavpack_parse_chain), (gst_wavpack_parse_sink_activate),
(gst_wavpack_parse_sink_activate_pull):
* ext/wavpack/gstwavpackparse.h:
Patch by: Sebastian Dröge <slomo at circular-chaos.org>
Make wavpackparse also work in push-mode (not seekable yet though);
some small clean-ups along the way; add support for SEEKING query
and query types function. (#351495).