avformat/concatdec: pass the interrupt callback on

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Fix decoding grayscale msrle.

Fixes ticket #3378.
Fix grayscale 8bps decoding.

Possible regression since 691dec62, no sample known.
Fix decoding of 32bit rawvideo in mov.

Fixes ticket #3377.