Original commit message from CVS:
* gst/matroska/Makefile.am:
* gst/matroska/matroska-demux.c: (gst_matroska_demux_add_stream),
(gst_matroska_demux_handle_src_event):
* gst/matroska/matroska-ids.c:
(gst_matroska_track_init_video_context),
(gst_matroska_track_init_audio_context),
(gst_matroska_track_init_subtitle_context),
(gst_matroska_track_init_complex_context):
* gst/matroska/matroska-ids.h:
Handle case where the TrackType ebml chunk does not come before the
TrackInfoAudio or TrackInfoVideo ebml chunk (#339446). Ignore QoS
events.
