Revert r132539 for now, "My testing shows that function stat has no problem...

Revert r132539 for now, "My testing shows that function stat has no problem with trailing separators. (tested on Windows and Darwin)."

It caused PR10331. MSVCRT stat() cannot strip trailing '/'. (can '\')

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@144884 91177308-0d34-0410-b5e6-96231b3b80d8