Fixed APIENTRY quirk with GLEW

libobs-opengl/gl-subsystem.h

@@ -20,11 +20,17 @@
 #include <util/darray.h>
 #include <graphics/graphics.h>
 #include <graphics/matrix4.h>
+
 #ifdef GLEW_STATIC
 #include "glew/include/GL/glew.h"
 #else
 #include <GL/glew.h>
 #endif
+
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
 #include "gl-helpers.h"
 #include "gl-exports.h"