Test exception spec compatibility on return type and parameters.

Along the way, use RequireCompleteType when testing exception spec types.
Separate all the ugly spec stuff into its own file.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@83764 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed