move platform specific codes to platform header

include/cglm-opengl.h

@@ -8,26 +8,9 @@
 #ifndef cglm_mat_opengl_h
 #define cglm_mat_opengl_h
 
-#ifdef __APPLE__
-#  include <OpenGL/gl3.h>
-#else
-#  ifdef _WIN32
-#    include <windows.h>
-#  endif
-#  include <GL/gl.h>
-#endif
-
+#include "cglm-platform.h"
 #include "cglm.h"
 
-#ifdef _WIN32
-extern
-void
-glUniformMatrix4fv(GLint location,
-                   GLsizei count,
-                   GLboolean transpose,
-                   const GLfloat *value);
-#endif
-
 CGLM_INLINE
 void
 glm_mat4_uniform(mat4 m, GLint location){