Windows: Add Hard Link support to AFS Redirector

Windows: Add Hard Link support to AFS Redirector

Both Windows and AFS support the notion of hard links to files.
Add an implementation to the AFS redirector.  The body of the
functionality and the IOCTL to the service permits the specification
of hard links to files across directory boundaries.  There is a
restriction within AFSSetFileLinkInfo() which prevents cross-directory
requests.  However, this can be taken out if AFS ever permits them.

Decrement object information link counts on directory entry
deletions.  Do not delete object information context blocks if the
link count is greater than 0.  Increment link counts when hard
links are added.

A subsequent patchset will implement the afsd_service support.

Change-Id: Iffabf480c0b43ab76feb5bdf3464a0bf1324e642
Reviewed-on: http://gerrit.openafs.org/8481
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>