Added deprecation warning for gcc

include/opencv/cv.h

@@ -43,8 +43,13 @@
 #ifndef __OPENCV_OLD_CV_H__
 #define __OPENCV_OLD_CV_H__
 
-#pragma warning("This is a deprecated opencv header provided for compatibility. Please \
+#if defined(__GNUC__)
-include a header from a corresponding opencv module")
+#warning "This is a deprecated opencv header provided for compatibility. Please include a header from a corresponding opencv module"
+#endif
+
+#if !defined(CV_IMPL)
+#define CV_IMPL extern "C"
+#endif //CV_IMPL
 
 #include "opencv2/core/core_c.h"
 #include "opencv2/core/core.hpp"