Add additional NEWS entries for 1.6.0pre5 through 1.6.0pre7

Add additional NEWS entries for 1.6.0pre5 through 1.6.0pre7

Taken from the release notes.  Do a bit of minor combining of related
issues since NEWS presents these all as changes in 1.6.0.

Reviewed-on: http://gerrit.openafs.org/5044
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit e06931172eec5a683490040f5564b294d263dac4)

Change-Id: I0fbd566258eec2f5d2664acf40289c4d6c544ee7
Reviewed-on: http://gerrit.openafs.org/5045
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>