Update gfxGLWindowTarget.h

Engine/source/gfx/gl/gfxGLWindowTarget.h

@@ -30,6 +30,8 @@ class GFXGLWindowTarget : public GFXWindowTarget
 public:
 
    GFXGLWindowTarget(PlatformWindow *win, GFXDevice *d);
+   ~GFXGLWindowTarget();
+
    const Point2I getSize() 
    { 
       return mWindow->getClientExtent();
@@ -64,4 +66,4 @@ private:
    void _WindowPresent();
 };
 
-#endif
+#endif