Update NEWS for 1.6.5.1

Release notes for 1.6.5.1 .

Change-Id: I06ae7a885f59b1b38fc21b27b57b3d843c203a73
Reviewed-on: http://gerrit.openafs.org/10316
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: Stephan Wiesand <stephan.wiesand@desy.de>