allow to compile and run the ExampleBrowser on older Mac OSX versions (without OpenGL3)

using the 'NO_OPENGL3' preprocessor definition
both premake/cmake has support for this now
needs some testing

examples/OpenGLWindow/GLPrimitiveRenderer.cpp

@@ -1,3 +1,4 @@
+#ifndef NO_OPENGL3
 #include "GLPrimitiveRenderer.h"
 #include "GLPrimInternalData.h"
 
@@ -319,4 +320,5 @@ void GLPrimitiveRenderer::setScreenSize(int width, int height)
 	m_screenWidth = width;
 	m_screenHeight = height;
     
-}
+}
+#endif