Ignore noreturn when checking function template specializations

As requested when applying the same logic to calling conventions.

Reviewers: rsmith

Differential Revision: http://llvm-reviews.chandlerc.com/D1634

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190441 91177308-0d34-0410-b5e6-96231b3b80d8