avformat/utils: support more AVC Intra formats without SPS/PPS header

add support for AVC Intra 50 720p and 1080p without SPS/PPS header in mxf and mov demuxers. I got the SPS/PPS tables from libbmx.

Reviewed-by: tomas.hardin@codemill.se
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>