[TIMOB-24404] Titanium projects specify "global.global != global" different

One of the users of the [RxJS](https://github.com/ReactiveX/rxjs) library reported that Appcelarator doesn't define global.global = global like node.js does. Since node.js doesn't have an official spec, I can't link to this behavior (it's also not documented best I can tell) but it was almost certainly borrowed from the fact that in browsers window.window = window--[that's spec'd here](https://html.spec.whatwg.org/multipage/browsers.html#the-window-object). Since appcelerator says it has [full node.js support](http://docs.appcelerator.com/platform/latest/#!/guide/Node.js_Support) minus some documented caveats, we were wondering if it would be easy and acceptable to also have global.global = global? Note that RxJS not the only library using global.global == global checks. There are [many](https://www.npmjs.com/package/window-or-global). It's mostly done to confirm we're not accidentally using a variable that happens to be named global but isn't really what we're looking for. Separately, we're going to discuss whether we could relax this check--but I think appcelerator would benefit from defining it regardless, cause others rely on it. RxJS issue: https://github.com/ReactiveX/rxjs/issues/2366