gst/matroska/matroska-mux.c: We need to drop one additional buffer for FLAC as the fLaC marker and STREAMINFO block a...

Original commit message from CVS:
* gst/matroska/matroska-mux.c:
(gst_matroska_mux_handle_sink_event),
(flac_streamheader_to_codecdata):
We need to drop one additional buffer for FLAC as the fLaC
marker and STREAMINFO block are merged into one buffer in the caps.
Also don't pretend to support NEWSEGMENT events, otherwise we
will most probably write some invalid data.