Preliminary release notes for 1.6.3

Change-Id: Ie4a6a984cfd9b819b0a3170acce7817998307157
Reviewed-on: http://gerrit.openafs.org/9859
Reviewed-by: Ken Dreyer <ktdreyer@ktdreyer.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>