Reland "Fix miscompile of MS inline assembly with stack realignment"

This re-lands commit r196876, which was reverted in r196879.

The tests have been fixed to pass on platforms with a stack alignment
larger than 4.

Update to clang side tests will land shortly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196939 91177308-0d34-0410-b5e6-96231b3b80d8
Fix gcc warnings.

Unused variable and unused typedef in release build.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196947 91177308-0d34-0410-b5e6-96231b3b80d8