h264: check chroma_format_idc range.

Fixes Ticket758
Bug found by: Diana Elena Muscalu
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/h264_ps.c

@@ -347,6 +347,10 @@ int ff_h264_decode_seq_parameter_set(H264Context *h){
 
     if(sps->profile_idc >= 100){ //high profile
         sps->chroma_format_idc= get_ue_golomb_31(&s->gb);
+        if (sps->chroma_format_idc > 3U) {
+            av_log(h->s.avctx, AV_LOG_ERROR, "chroma_format_idc %d is illegal\n", sps->chroma_format_idc);
+            goto fail;
+        }
         if(sps->chroma_format_idc == 3)
             sps->residual_color_transform_flag = get_bits1(&s->gb);
         sps->bit_depth_luma   = get_ue_golomb(&s->gb) + 8;