gst/qtdemux/qtdemux.c: Cleanups.  Convert g_prints to GST_LOGs.  Add qtdemux debug category.  Attempt to fix timestam...

Original commit message from CVS:
* gst/qtdemux/qtdemux.c: (plugin_init), (gst_qtdemux_loop_header),
(qtdemux_parse_moov), (qtdemux_parse), (qtdemux_node_dump_foreach),
(qtdemux_dump_mvhd), (qtdemux_dump_tkhd), (qtdemux_dump_elst),
(qtdemux_dump_mdhd), (qtdemux_dump_hdlr), (qtdemux_dump_vmhd),
(qtdemux_dump_dref), (qtdemux_dump_stsd), (qtdemux_dump_stts),
(qtdemux_dump_stss), (qtdemux_dump_stsc), (qtdemux_dump_stsz),
(qtdemux_dump_stco), (qtdemux_dump_co64), (qtdemux_dump_dcom),
(qtdemux_dump_cmvd), (qtdemux_parse_tree), (qtdemux_parse_trak):
Cleanups.  Convert g_prints to GST_LOGs.  Add qtdemux debug
category.  Attempt to fix timestamp calculation.