Non-delegated events are now correctly raised on html widgets

This pull request fixes the following issue: non-delegated events were not raised on html widgets (the event mechanism implemented in `aria.html.Element` did no check whether events were delegated or not).

With this fix, if an event is not delegated, the fallback markup is added so that the handler is correctly called.

Especially, the `onchange` event on the html select widget is now correctly raised on IE 7-10, which fixes `test.aria.html.select.onchange.DataModelOnChangeTestCase`.