Ported from :https://typescript.codeplex.com/workitem/1085

Some core ambientvars already do this when theonly interface is the static one e.g.JSON :https://github.com/Microsoft/TypeScript/blob/master/src/lib/core.d.ts#L916-L959

Would be nice to do the name for others likeString,Date perhaps calling themStringStatic andDateStatic. It is need for definitions for quite a few JavaScript libraries.