OpenBSD: Add config headers for new(er) OS versions.

The OS-specific config header files have not kept up with the
newer releases of OpenBSD. This patch corrects that by adding
header files for OpenBSD versions from 4.9 to 5.3 (the newest
version currently under development).

Reviewed-on: http://gerrit.openafs.org/8927
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 20a54b02521b40b07e4ec87df55a1e9a2549c881)

Change-Id: I9ee66dbba300d5a68bc294a14dd9463441143371
Reviewed-on: http://gerrit.openafs.org/9661
Reviewed-by: Simon Wilkinson <simonxwilkinson@gmail.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: BuildBot <buildbot@rampaginggeek.com>