Fix GLAPIENTRY re-definition warning on OpenBSD

Closes #1039.

include/GLFW/glfw3.h

@@ -107,12 +107,6 @@ extern "C" {
  #endif
 #endif /* APIENTRY */
 
-/* Some OpenGL related headers use GLAPIENTRY instead.
- */
-#ifndef GLAPIENTRY
- #define GLAPIENTRY APIENTRY
-#endif /* GLAPIENTRY */
-
 /* Some Windows OpenGL headers need this.
  */
 #if !defined(WINGDIAPI) && defined(_WIN32)
@@ -215,6 +209,9 @@ extern "C" {
  #endif /*__APPLE__*/
 
 #endif /* OpenGL and OpenGL ES headers */
+#ifndef GLAPIENTRY
+ #define GLAPIENTRY APIENTRY
+#endif /* GLAPIENT
 
 #if defined(GLFW_INCLUDE_VULKAN)