Windows: Use Microsoft IO_REPARSE_TAG_SYMLINK tag

For symlinks and DFS Links use Microsoft's NTFS Symlink tag,
IO_REPARSE_TAG_SYMLINK, instead of the OpenAFS assigned tag.

The DeleteFile() and RemoveDirectory() Win32 APIs do not delete
non-Microsoft reparse points and instead delete the target object.
While it is possible for Take Command and potentially Cygwin to
alter their behavior with AFS specific knowlege, it is not possible
to alter the Explorer Shell, cmd.exe and powershell.

Using the Microsoft tag is a violation of Microsoft policy.

Change-Id: I90a419fe21637bb871d08528463d1178078a9947
Reviewed-on: http://gerrit.openafs.org/9497
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>