avcodec/huffman: use av_malloc_array()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/ratecontrol: use av_malloc_array()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/tiff: use av_malloc(z)_array()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcdoec/webp: use av_malloc_array()

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