Bug 1052243 - jshangul.js need unit tests

I write unit tests for 'jshangul.js'.
Please do:

    require('/test/unit/setup_engine.js');
    require('/js/imes/jshangul/jshangul.js');

`setup_engine.js` is actually going away (I have a local patch on a unfiled bug), but I think I can remove that ref altogether.