mov: Support empty first edit + normal second edit.
mov: Support roll recovery grouping.

Frames that are a starting point of recovery are treated as keyframe and have non-zero distance since themselves are an incomplete frame.
This is useful for random accessing stream with gradual decoder refresh.
avcodec: Add output picture number to AVCodecParserContext.
h264_parser: Set output_picture_number.
dirac_parser: Set output_picture_number.