C-API cleanup: backport videoio changes from 5.x

modules/core/include/opencv2/core/cvdef.h

@@ -928,6 +928,17 @@ typedef hfloat float16_t;
 }
 #endif
 
+/** @brief Constructs the 'fourcc' code, used in video codecs and many other places.
+    Simply call it with 4 chars like `CV_FOURCC('I', 'Y', 'U', 'V')`
+*/
+CV_INLINE int CV_FOURCC(char c1, char c2, char c3, char c4)
+{
+    return (c1 & 255) + ((c2 & 255) << 8) + ((c3 & 255) << 16) + ((c4 & 255) << 24);
+}
+
+//! Macro to construct the fourcc code of the codec. Same as CV_FOURCC()
+#define CV_FOURCC_MACRO(c1, c2, c3, c4) (((c1) & 255) + (((c2) & 255) << 8) + (((c3) & 255) << 16) + (((c4) & 255) << 24))
+
 //! @}
 
 #ifndef __cplusplus