gst/qtdemux/qtdemux.c: Added full edit list support.

gst/qtdemux/qtdemux.c: Added full edit list support.

Original commit message from CVS:
* gst/qtdemux/qtdemux.c: (gst_qtdemux_init),
(gst_qtdemux_handle_src_query), (gst_qtdemux_find_index),
(gst_qtdemux_find_keyframe), (gst_qtdemux_find_segment),
(gst_qtdemux_move_stream), (gst_qtdemux_perform_seek),
(gst_qtdemux_do_seek), (gst_qtdemux_change_state),
(gst_qtdemux_activate_segment),
(gst_qtdemux_prepare_current_sample), (gst_qtdemux_advance_sample),
(gst_qtdemux_loop_state_movie), (gst_qtdemux_loop),
(qtdemux_parse_trak):
Added full edit list support.
Avoid overflows in prologue image detection code.
Avoid roundoff errors in timestamp calculations.