Original commit message from CVS:
* gst/qtdemux/qtdemux.c: (gst_qtdemux_go_back),
(gst_qtdemux_perform_seek), (gst_qtdemux_do_seek),
(gst_qtdemux_loop_state_movie), (gst_qtdemux_loop),
(gst_qtdemux_chain), (qtdemux_parse_tree), (qtdemux_parse_trak):
More cleanups, added comments.
Mark discontinuities on outgoing buffers.
Post better errors when something goes wrong.
Handle EOS and segment end properly.