vf_libopencv: replace opencv/cxtypes.h #include by opencv/cxcore.h

cxtypes.h works with version 2.1 and older, cxcore.h works with 2.2 and older.
Signed-off-by: Diego Biurrun <diego@biurrun.de>

libavfilter/vf_libopencv.c

@@ -26,7 +26,7 @@
 /* #define DEBUG */
 
 #include <opencv/cv.h>
-#include <opencv/cxtypes.h>
+#include <opencv/cxcore.h>
 #include "libavutil/avstring.h"
 #include "libavutil/file.h"
 #include "avfilter.h"