mpegvideo: initialize dummy reference frames.

Do not rely on get_buffer initializing them.

Changes yadif tests (off by one in one border pixel), because yadif
reads from those uninitialized lines.
Merge remote-tracking branch 'qatar/master'

* 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>
Fate test to print side_data crc if present

Modified the fate test crc generator to print the side_data's
crc if side_data is present.

Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
framecrcenc: Also print the size of side data elements

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
framecrcenc: print all side data elements, not just the first

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>