fix compilation with clang-cl

__stdcall is supported by MinGW as well.

Author: neheb

source/glbinding/include/glbinding/gl/types.h

@@ -10,8 +10,8 @@
 #include <KHR/khrplatform.h>
 
 
-#ifdef _MSC_VER
-#define GL_APIENTRY __stdcall
+#ifdef WINAPI
+#define GL_APIENTRY WINAPI
 #else
 #define GL_APIENTRY
 #endif
@@ -99,4 +99,4 @@ struct _cl_event;
 } // namespace gl
 
 
-#include <glbinding/gl/types.inl>
+#include <glbinding/gl/types.inl>