Fix type mismatch assertion related to inalloca and PR19287

Augment the test case from r205217 to catch this related bug.

Fixes the Windows self-host which was failing on VariantValue.cpp.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@205378 91177308-0d34-0410-b5e6-96231b3b80d8