fix: don’t use the global ng at all with closure enhanced optimizations

This is needed as:
- closure declares globals itself for minified names, which sometimes clobber our `ng` global
- we can't declare a closure extern as the namespace `ng` is already used within Google for typings for angularJS (via `goog.provide('ng....')`).

packages/types.d.ts

@@ -15,3 +15,4 @@
 /// <reference path="../node_modules/@types/selenium-webdriver/index.d.ts" />
 /// <reference path="./es6-subset.d.ts" />
 /// <reference path="./system.d.ts" />
+/// <reference path="./goog.d.ts" />