Support standardized DOM WheelEvent

Originally reported on Google Code with ID 8012

```
Currently GWT 2.5 supports only old mousewheel and DOMMouseScroll events and there is
a lack of supporting standardized WheelEvent:

https://developer.mozilla.org/en-US/docs/Mozilla_event_reference/wheel
http://www.w3.org/TR/DOM-Level-3-Events/#event-type-wheel

```

Reported by `a.korzhevskiy` on 2013-02-14 12:17:27
