Windows: Add Hard Link support to Service

Windows: Add Hard Link support to Service

Implement Hard Link support to the redirector interface in the
service.  It is implemented to support hard links across directories
even though AFS does not currently support it.  cm_Link() will
check before issuing an RPC to the file server.   ReplaceIfExists
functionality is implemented by cm_Unlink() followed by cm_Link()
if required.

Change-Id: Icb4e7eeaed1ae57719c487fe3bf29efea1902246
Reviewed-on: http://gerrit.openafs.org/8482
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>