gst/mxf/: Implement parsing of the random index pack, which provides a seek table...

gst/mxf/: Implement parsing of the random index pack, which provides a seek table (including body sid) to the start o...

Original commit message from CVS:
* gst/mxf/mxfdemux.c: (gst_mxf_demux_reset),
(gst_mxf_demux_handle_random_index_pack),
(gst_mxf_demux_pull_random_index_pack), (gst_mxf_demux_loop):
* gst/mxf/mxfdemux.h:
* gst/mxf/mxfparse.c: (mxf_random_index_pack_parse):
* gst/mxf/mxfparse.h:
* gst/mxf/mxftypes.h:
Implement parsing of the random index pack, which provides a seek
table (including body sid) to the start of partition packs.
Later this will be used for reading all index table segments of
the complete file efficiently.