gst/mpegdemux/gstmpegdemux.*: The position member in the newsegment event corresponds to the stream_time of the segme...

Original commit message from CVS:
* gst/mpegdemux/gstmpegdemux.c: (gst_flups_demux_send_data):
* gst/mpegdemux/gstmpegdemux.h:
The position member in the newsegment event corresponds to the
stream_time of the segment start position.