Include st_dev to make the result of getUniqueID actually unique.

This will let us use getUniqueID instead of st_dev directly on clang.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187378 91177308-0d34-0410-b5e6-96231b3b80d8
Delete documentation for deleted options.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187380 91177308-0d34-0410-b5e6-96231b3b80d8
Make file_status::getUniqueID const.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187383 91177308-0d34-0410-b5e6-96231b3b80d8