Fixes or IE

I honestly don't know how IE < 9 was ever testing successfully. This PR corrects a few minor issues and one issue with our internal `trigger` method with overloaded args. Again, not really sure how that ever worked, but this should fix it.

Reviews appreciated (@dcneiner @jcreamer898 @whoeverelse)
From what I can tell, this internal method is only used twice, and the special test for context is only needed on this:

```js
if ( requestSettings.global ) {
			trigger(requestSettings, "ajaxSuccess", [{}, requestSettings] );
		}
```

I'd recommend changing the other usage (below) directly to $.event.trigger and revert this function to the original code.

```js
$.even.trigger( "ajaxComplete", [{}, requestSettings] );
```