OpenGL: generic inputs for new matrix API

For functions that expect a 4x4 matrix, you can pass in that, or array[16], or float*, or... Casting at each call site can get annoying, and obscures the logic.

The C11 section still needs work, but the non-C11 macros help on the system I tested on (Mac/clang).

Part of T49450

source/blender/gpu/intern/gpu_matrix.c

@@ -29,6 +29,7 @@
  *  \ingroup gpu
  */
 
+#define SUPPRESS_GENERIC_MATRIX_API
 #include "GPU_matrix.h"
 
 #include "BLI_math_matrix.h"