Introduce a bit into Type that keeps track of whether there are any

unnamed or local types within that type. This bit is cached along with
the linkage of a type, so that it can be recomputed (e.g., when we see
that a typedef has given a name to an anonymous declaration).

Use this bit when checking C++03 [temp.arg.type]p2, so that we don't
walk template argument types repeatedly.

llvm-svn: 116413