MS ABI: Don't push destructor cleanups for aggregate parameters in thunks

The target method of the thunk will perform the cleanup.  This can't be
tested in 32-bit x86 yet because passing something by value would create
an inalloca, and we refuse to generate broken code for that.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213976 91177308-0d34-0410-b5e6-96231b3b80d8