Fix problem with Parcel reload

Parcel uses "hot module replacement" (HMR), which has quite intuitive
problems with `requestAnimationFrame`-based animation:
parcel-bundler/parcel#289

We now use a pretty ridiculous hack to cancel previous animation loops
when setting up new ones for our examples.

examples/lglexample.ts

@@ -294,7 +294,7 @@ export function setup(canvas: HTMLCanvasElement, render: (view: mat4, projection
   gl.clear(gl.COLOR_BUFFER_BIT);
 
   // Set up the render loop.
-  registerAnimator(() => {
+  let cancel = registerAnimator(() => {
     // Update the camera view.
     camera.view(view);
     camera.tick();
@@ -314,6 +314,13 @@ export function setup(canvas: HTMLCanvasElement, render: (view: mat4, projection
     render(view, projection);
   });
 
+  // A **total hack** to cancel previously-registered animation loops.
+  let w = window as any;
+  if (w._linguineCancel) {
+    w._linguineCancel();
+  }
+  w._linguineCancel = cancel;
+
   return gl;
 }