Windows: disable Adv ICF support if not supported

Windows: disable Adv ICF support if not supported

OpenAFS 1.6.x does not require the use of SDK 6.0 or above.
Therefore the Advanced Internet Connection Firewall support
may not be available.  In particular, the 32-bit distribution
for 1.6.x does not rely on SDK 6.0 or higher.

This is a 1.6.x only change.

Change-Id: I8ab5bbf4c5d6e4893d5389c04ec020114a3d5683
Reviewed-on: http://gerrit.openafs.org/6841
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>