vf_libopencv: prefer opencv/cxcore.h over cxtypes.h

Require the presence of opencv/cxcore.h in place of opencv/cxtypes.h,
which has been removed. Fix compilation with libopencv > 2.1.0.

Fix trac issue #221.

configure

@@ -2919,7 +2919,7 @@ enabled libmp3lame && require  "libmp3lame >= 3.98.3" lame/lame.h lame_set_VBR_q
 enabled libnut     && require  libnut libnut.h nut_demuxer_init -lnut
 enabled libopencore_amrnb  && require libopencore_amrnb opencore-amrnb/interf_dec.h Decoder_Interface_init -lopencore-amrnb
 enabled libopencore_amrwb  && require libopencore_amrwb opencore-amrwb/dec_if.h D_IF_init -lopencore-amrwb
-enabled libopencv  && require_pkg_config opencv opencv/cv.h cvCreateImageHeader
+enabled libopencv  && require_pkg_config opencv opencv/cxcore.h cvCreateImageHeader
 enabled libopenjpeg && require libopenjpeg openjpeg.h opj_version -lopenjpeg
 enabled librtmp    && require_pkg_config librtmp librtmp/rtmp.h RTMP_Socket
 enabled libschroedinger && require_pkg_config schroedinger-1.0 schroedinger/schro.h schro_init

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"