Instead friending status, provide windows and posix constructors to file_status.

This opens the way of having static helpers in the .inc files that can
construct a file_status.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186376 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed