gst/qtdemux/: QtDemux can now work push-based.

gst/qtdemux/: QtDemux can now work push-based.

Original commit message from CVS:
* gst/qtdemux/Makefile.am:
* gst/qtdemux/qtdemux.c: (gst_qtdemux_init),
(gst_qtdemux_handle_sink_event), (gst_qtdemux_change_state),
(extract_initial_length_and_fourcc),
(gst_qtdemux_loop_state_header), (gst_qtdemux_loop_state_movie),
(gst_qtdemux_loop_header), (next_entry_size), (gst_qtdemux_chain),
(qtdemux_sink_activate), (qtdemux_sink_activate_pull),
(qtdemux_sink_activate_push), (qtdemux_parse_trak):
* gst/qtdemux/qtdemux.h:
QtDemux can now work push-based.
It still needs some love for seeking.