Src: Export Assert methods for backwards compatibility

Ref: https://github.com/jquery/qunit/pull/577#issuecomment-47281591

The tests are rude, but I couldn't think on anything better yet.
I think our convention is to use no leading space in directives. Searching the all public jQuery repositories yielded 0 matches for `/* global ` and 27 for `/*global `.

* https://github.com/search?l=javascript&q=%22%2Aglobal%22+%40jquery&ref=searchresults&type=Code
* https://github.com/search?l=javascript&q=%22%2A+global%22+%40jquery&ref=searchresults&type=Code