[ms-inline asm] Make this a hard error.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179865 91177308-0d34-0410-b5e6-96231b3b80d8
[ms-inline asm] Move this variable into the scope in which it is used.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179866 91177308-0d34-0410-b5e6-96231b3b80d8