chore(build): enable type-checking for TypeScript ES6 emit.

This requires delicate handling of type definitions which collide, because
we use TypeScript-provided lib.d.ts for --target=es5 and lib.es6.d.ts for
--target=es6.
We need to include our polyfill typings only in the --target=es5 case,
and the usages have to be consistent with lib.es6.d.ts.
Also starting with this change we now typecheck additional modules,
so this fixes a bunch of wrong typings which were never checked before.

Fixes #3178

modules/angular2_material/src/components/input/input.ts

@@ -49,7 +49,8 @@ export class MdInputContainer {
     // classes based on the input state.
     ObservableWrapper.subscribe(input.mdChange, value => { this.inputHasValue = value != ''; });
 
-    ObservableWrapper.subscribe(input.mdFocusChange, hasFocus => {this.inputHasFocus = hasFocus});
+    ObservableWrapper.subscribe<boolean>(input.mdFocusChange,
+                                         hasFocus => this.inputHasFocus = hasFocus);
   }
 }