Make OpenAFS 1.8.1

Make OpenAFS 1.8.1

Update version strings for the 1.8.1 release.
(Note that the version number for Windows for the 1.8.1 prereleases was
erroneously 1.8.99xx, when it should have been 1.8.00xx to reflect
"next after 1.8.0-final".)

Change-Id: I2ce32aeae50d80b88cbc3f73f6787e3a15747085
Reviewed-on: https://gerrit.openafs.org/13266
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>