gst/matroska/: Add support for VOBSUB subtitle tracks and zlib-compressed tracks...

gst/matroska/: Add support for VOBSUB subtitle tracks and zlib-compressed tracks. Make sure we start on a keyframe af...

Original commit message from CVS:
Patch by: Frédéric Riss  <frederic.riss at gmail dot com>
* gst/matroska/matroska-demux.c: (gst_matroska_track_free),
(gst_matroska_demux_reset),
(gst_matroska_demux_read_track_encodings),
(gst_matroska_demux_add_stream), (gst_matroska_decode_buffer),
(gst_matroska_demux_parse_blockgroup_or_simpleblock),
(gst_matroska_demux_subtitle_caps):
* gst/matroska/matroska-ids.h:
Add support for VOBSUB subtitle tracks and zlib-compressed
tracks. Make sure we start on a keyframe after a seek. (#343348)