Fix nalsize check to avoid an integer overflow that made the check

incorrect for nalsize >= INT_MAX


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@19307 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/h264.c

@@ -7505,7 +7505,7 @@ static int decode_nal_units(H264Context *h, const uint8_t *buf, int buf_size){
             nalsize = 0;
             for(i = 0; i < h->nal_length_size; i++)
                 nalsize = (nalsize << 8) | buf[buf_index++];
-            if(nalsize <= 1 || (nalsize+buf_index > buf_size)){
+            if(nalsize <= 1 || nalsize > buf_size - buf_index){
                 if(nalsize == 1){
                     buf_index++;
                     continue;