Dont cast const away.

Originally committed as revision 11700 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/crc.c

@@ -115,7 +115,7 @@ uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t le
 #ifndef CONFIG_SMALL
     if(!ctx[256])
         while(buffer<end-3){
-            crc ^= le2me_32(*(uint32_t*)buffer); buffer+=4;
+            crc ^= le2me_32(*(const uint32_t*)buffer); buffer+=4;
             crc =  ctx[3*256 + ( crc     &0xFF)]
                   ^ctx[2*256 + ((crc>>8 )&0xFF)]
                   ^ctx[1*256 + ((crc>>16)&0xFF)]