* qatar/master:
  mpegvideo: initialize dummy reference frames.

Conflicts:
	libavcodec/mpegvideo.c
	tests/ref/fate/filter-yadif-mode1

The luma init is left at 0x80 as it was previously, and tested and
working since a long time. Its also mandated to be 0x80 by at least
one specification. Cases that need different values already had
code in place to handle them.
Merged-by: Michael Niedermayer <michaelni@gmx.at>