Avcodec: set the cpu flags/mask in modern version of libavutil

modules/codec/avcodec/avcodec.c

@@ -329,6 +329,9 @@ static int OpenDecoder( vlc_object_t *p_this )
     p_context->debug = var_InheritInteger( p_dec, "avcodec-debug" );
     p_context->opaque = (void *)p_this;
     p_context->dsp_mask = GetVlcDspMask(); /* set CPU capabilities */
+#if LIBAVUTIL_VERSION_INT >= AV_VERSION_INT( 51, 25, 0 )
+    av_set_cpu_flags_mask( INT_MAX & ~p_context->dsp_mask );
+#endif
 
     p_dec->b_need_packetized = true;
     switch( i_cat )