src/bugsnag: implement own polyfilling for requestAnimationFrame

Fixes #72 (`requestAnimationFrame` wrapper doesn't honor the passed
timestamp)

The old approach rely on `hijackTimeFunc`, which expects a callback to
accept at least two arguments. If the function being wrapped accepts
only argument, it is being swallowed.

Tested manually on IE 6,7,8,9,10, and modern Chrome.
Correctly me if I'm wrong, but I think the following is the equivalent, but much less code;

```javascript
polyFill(window, "requestAnimationFrame", function (_super) {
  return function (callback) {
    if (typeof callback === "function") {
      callback = wrap(callback);
    }
    return _super(callback);
  };
});
```