Removed references and dependencies to winrt.d.ts.

@borisyankov, @arthurgreef

This is a change to decouple winrt.d.ts from winjs.d.ts since WinJS is going to be supported outside the context of a Windows 8 app.

The change itself introduces a very small loss in typing; two functions lose WinRT-specific type annotations on one of their parameters (WinJS.UI.StorageDataSource.ctor and WinJS.UI.SearchBox.setLocalContentSuggestionSettings).

Weaving in #2293, another option is to possibly maintain this as a separate winjs.d.ts file that is free of WinRT dependencies.