Windows: Add VIOC_GETUNIXMODE and VIOC_SETUNIXMODE

Windows: Add VIOC_GETUNIXMODE and VIOC_SETUNIXMODE

Add pioctls to get and set the UNIX mode bits for an
object in AFS.

Reviewed-on: http://gerrit.openafs.org/3545
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit 27469e59b134efef6c908a1bfa8162d4bf9b8275)

Change-Id: Id80cb41732a6daffa2f03a4313ef3cb9f94b87ea
Reviewed-on: http://gerrit.openafs.org/3802
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>