Add NEWS entries for OpenAFS 1.5.77 and 1.5.76

Add NEWS entries for OpenAFS 1.5.77 and 1.5.76

Based on the public announcement for 1.5.77.

Change-Id: Ic368e16e16b03a79de6196a2e355eca0f420de77
Reviewed-on: http://gerrit.openafs.org/2819
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 0a9e57c45e4412d9dac7050d693a22044ddc1d0f)
Reviewed-on: http://gerrit.openafs.org/2820
Reviewed-by: Russ Allbery <rra@stanford.edu>
Tested-by: Russ Allbery <rra@stanford.edu>
(cherry picked from commit c12a6ec003fef78ed869bb92e384dfacf02add98)