handdetect: Change gsthanddetect to C++

Change the gsthanddetect.c file to cpp and add it into Makefile.
It is necessary to migrate the handdetect plugin to C++,
in order to load new and old classifiers, to make handdetect work
with newer versions of Opencv.

https://bugzilla.gnome.org/show_bug.cgi?id=752528

ext/opencv/Makefile.am

@@ -13,7 +13,7 @@ libgstopencv_la_SOURCES = gstopencv.cpp \
 			gstcvsobel.c \
 			gstedgedetect.cpp \
 			gstfaceblur.cpp \
-			gsthanddetect.c \
+			gsthanddetect.cpp \
 			gstpyramidsegment.c \
 			gsttemplatematch.c \
 			gsttextoverlay.c \
@@ -27,7 +27,8 @@ libgstopencv_la_SOURCES = gstopencv.cpp \
 			motioncells_wrapper.cpp \
 			MotionCells.cpp
 
-libgstopencv_la_CXXFLAGS = $(GST_PLUGINS_BASE_CFLAGS) $(GST_BASE_CFLAGS) $(GST_CXXFLAGS) $(OPENCV_CFLAGS)
+libgstopencv_la_CXXFLAGS = $(GST_PLUGINS_BASE_CFLAGS) $(GST_BASE_CFLAGS) $(GST_CXXFLAGS) $(OPENCV_CFLAGS) \
+	-DGST_HAAR_CASCADES_DIR=\"$(pkgdatadir)/@GST_API_VERSION@/opencv_haarcascades\"
 
 # flags used to compile this facedetect
 # add other _CFLAGS and _LIBS as needed
@@ -36,7 +37,6 @@ libgstopencv_la_CXXFLAGS = $(GST_PLUGINS_BASE_CFLAGS) $(GST_BASE_CFLAGS) $(GST_C
 # OpenCV's define isn't good enough to avoid 'unused' gcc warnings (at v2.1.0)
 libgstopencv_la_CFLAGS = $(GST_PLUGINS_BASE_CFLAGS) $(GST_BASE_CFLAGS) \
 	$(GST_CFLAGS) $(OPENCV_CFLAGS) \
-	-DGST_HAAR_CASCADES_DIR=\"$(pkgdatadir)/@GST_API_VERSION@/opencv_haarcascades\" \
 	-DCV_INLINE="static inline" \
 	-DCV_NO_BACKWARD_COMPATIBILITY