make examples compile, code that accessed window & graphics via the callback is currently disabled, until that is added back in

examples3d/platform3.rs

@@ -65,7 +65,7 @@ pub fn init_world(testbed: &mut Testbed) {
      * Setup a callback to control the platform.
      */
     let mut count = 0;
-    testbed.add_callback(move |_, physics, _, _, run_state| {
+    testbed.harness_mut().add_callback(move |physics, _, run_state, _| {
         count += 1;
         if count % 100 > 50 {
             return;