Export comerr initialization functions from libafsauthent

Export comerr initialization functions from libafsauthent

Add to the libafsauthent export symbol list these comerr initialization
functions so that they are usable by consumers.

Reviewed-on: https://gerrit.openafs.org/13055
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Anders Kaseorg <andersk@mit.edu>
Tested-by: Anders Kaseorg <andersk@mit.edu>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit 70c4922980d1596155b4021cd72d6895c2371e23)

Change-Id: I7fb91b14c0730abd8544ff0484af8746c2bb50db
Reviewed-on: https://gerrit.openafs.org/13142
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>