Windows: Service processing for Symlink creation

Initial support for symlink creation via the Win32 CreateSymbolicLink api.
Add support for AFS_REQUEST_TYPE_CREATE_SYMLINK redirector requests via
the new RDR_CreateSymlinkEntry() function.

Since CreateSymbolicLink api creates a new directory or file object and
then assigns the Microsoft reparse tag data to that object,
RDR_CreateSymlinkEntry must first delete the empty directory or file and
then create the new symlink object in its place.  If the empty object can
be removed but the symlink cannot be created, STATUS_FILE_DELETED is
returned to indicate to the redirector that a failure occurred that
changed the state of the directory without creating a new object.

If the empty object cannot be removed, a STATUS_ACCESS_DENIED error will
be returned and the empty object will unfortunately remain in the AFS
directory.

Target path translation is performed.  Absolute AFS paths are stored in
UNIX notation.  Absolute non-AFS UNC and device paths are prefaced with
"msdfs:".

Change-Id: If8b4729dd5fffddc71221750852b8be731c83cab
Reviewed-on: http://gerrit.openafs.org/9425
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>
Windows: RDR_UpdateFile dscp != scp

Do not set bScpLocked when obtaining scp->rw as scp != dscp.

Change-Id: I878166cd510a188a0e56cc92660e74b9625c3ab6
Reviewed-on: http://gerrit.openafs.org/9553
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>