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

examples2d/platform2.rs

@@ -60,7 +60,7 @@ pub fn init_world(testbed: &mut Testbed) {
     /*
      * Setup a callback to control the platform.
      */
-    testbed.add_callback(move |_, physics, _, _, run_state| {
+    testbed.harness_mut().add_callback(move |physics, _, run_state, _| {
         let platform = physics.bodies.get_mut(platform_handle).unwrap();
         let mut next_pos = *platform.position();