Original commit message from CVS:
* gst/qtdemux/qtdemux.c: (gst_qtdemux_get_duration),
(qtdemux_parse_samples), (qtdemux_parse_segments),
(qtdemux_parse_trak), (qtdemux_parse_tree):
* gst/qtdemux/qtdemux_dump.c: (qtdemux_dump_mdhd):
Handle version 1 mdhd atoms to get extended precision durations.
Fixes #426972.