Fix declaring class template methods with an attributed typedef

Summary:
VisitFunctionDecl had some logic for attempting to handle this case.  I
reused for class template methods.  Instantiation still fails, but at
least now clang doesn't crash.

With AttributedTypes for these function attributes, we should be able to
make this work without losing the typedef sugar.

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1135