avformat/matroskadec: use av_realloc_array()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/matroskaenc: use av_realloc_array()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/mxfdec: use av_realloc_array()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/utils: use av_realloc_array()

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