Issue 7819 - setTimes should support folders on Windows

http://d.puremagic.com/issues/show_bug.cgi?id=7819

- Moved setTimes implementation closer to getTimes.

- Added `FILE_FLAG_BACKUP_SEMANTICS` and `FILE_ATTRIBUTE_DIRECTORY` flags to enable setting folder times on Windows (See MSDN docs for these [here](http://msdn.microsoft.com/en-us/library/windows/desktop/aa363858%28v=vs.85%29.aspx)).

- Updated getTimes docs to reflect it works on folders.

- Changed `enforce` to `cenforce` for Posix in `setTimes` since the function claimed it only threw `FileException`'s.