hevc: replace av_malloc+memset with av_mallocz

Conflicts:
	libavcodec/hevc.c
hevc: redistribute malloc failure checks to their corresponding mallocs
hevc: drop checks on freeing a NULL pointer

Conflicts:
	libavcodec/hevc.c
hevc: replace sizeof(type) with sizeof(var)
hevc: reformat pred_weight_table()
hevc: decode RADL frames.