libafsrpc: export some more rx functions

libafsrpc: export some more rx functions

Reviewed-on: https://gerrit.openafs.org/13138
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 0b1edd96ac7a952148ec14f8baaf60c8d8bbc04f)

Change-Id: I86c81dd95c75953ebd193bd8b49b467693572614
Reviewed-on: https://gerrit.openafs.org/13194
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Joe Gorse <jhgorse@gmail.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Marcio Brito Barbosa <mbarbosa@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>