Update NEWS for 1.6.5.2

Release notes for 1.6.5.2

Change-Id: I59f5aa9a6887e3d23288672a08e67e0d676e239c
Reviewed-on: http://gerrit.openafs.org/10587
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: Stephan Wiesand <stephan.wiesand@desy.de>