Call ResolveExceptionSpec for non-OdrUsed functions.

In C++11, instantiation of exception specs is deferred. The instantiation is
done in MarkFunctionReferenced(), which wasn't called for non-OdrUsed functions,
which then caused an assert in codegen. Fixes PR19190, see the bug for details.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@216562 91177308-0d34-0410-b5e6-96231b3b80d8