Sort the rfc3961 library's export symbol list

It was originally committed in an unsorted state.

Change-Id: Ife43b60cd625eae5062865942fc5c8956d6b6aab
Reviewed-on: http://gerrit.openafs.org/10583
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Perry Ruiter <pruiter@sinenomine.net>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>