Further tweak -Wurneachable-code and templates by allowing the warning to run on
explicit template specializations (which represent actual functions somebody wrote).

Along the way, refactor some other code which similarly cares about whether or
not they are looking at a template instantiation.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145547 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed