cmdutils: include config.h, fix "is not defined" warning due to CONFIG_OPENCL

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

cmdutils.h

@@ -24,6 +24,7 @@
 
 #include <stdint.h>
 
+#include "config.h"
 #include "libavcodec/avcodec.h"
 #include "libavfilter/avfilter.h"
 #include "libavformat/avformat.h"