[ms-cxxabi] Remove unused variable

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178550 91177308-0d34-0410-b5e6-96231b3b80d8
[ms-cxxabi] Rename enum and remove dead case per Jordan's suggestion

The IHM_ prefix was a fairly gross abbreviation to try to hit three
characters for uniqueness.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178551 91177308-0d34-0410-b5e6-96231b3b80d8
Moved fallthrough regression test to switch-implicit-fallthrough.cpp.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178554 91177308-0d34-0410-b5e6-96231b3b80d8