[#33962] Use a proxy function to close modals.

Because otherwise, we will always be stuck with SqueezeBox/Mootools.

Tracker: http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33962&start=0
@roland-d That's not what I mean. Look again. The change just makes the string cleaner by using double quotes instead of escaped single quotes (this whole thing is a single-quoted php string). What we're looking at is something like this:

```javascript
var x = "some string" + ("some other string", someVar);
```
which is really the same as:
```javascript
var x = "some string" + someVar;
```

So why is it like this? Am I missing something or is this just some nonsense?