Revert "[-cxx-abi microsoft] Mangle reference temporaries"

This reverts commit r197184.

Richard Smith brings up some good points, a proper implementation will
require us to mangle unnameable entities compatibly with MSVC.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197192 91177308-0d34-0410-b5e6-96231b3b80d8