[change-namespace] consider typedef/using alias decls in the moved namespace.

Summary: If a TypeLoc refers to a type alias defined in the moved namespace, we do not need to update its specifier since the type alias decl will be moved along with the type reference.

Reviewers: hokein

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D26592

llvm-svn: 286873