Original commit message from CVS:
* gst/mve/gstmvedemux.c: (gst_mve_demux_get_src_query_types),
(gst_mve_demux_handle_src_query), (gst_mve_demux_handle_src_event),
(gst_mve_add_stream):
Support SEEKING query (bad news now delivered properly!); add event
function to source pads to make sure seeks aren't propagated
upstream, even if they aren't handled.