Export {Get,Set}ServiceSpecific from liboafs_rx.la

Export {Get,Set}ServiceSpecific from liboafs_rx.la

rxgk will use service-specific data.

Reviewed-on: https://gerrit.openafs.org/10589
Reviewed-by: Daria Phoebe Brashear <dariaphoebe@auristor.com>
Reviewed-by: Chas Williams <3chas3@gmail.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Marcio Brito Barbosa <mbarbosa@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit 60a006bdc43df42e40eb43f1e1af7fffe3e85763)

Change-Id: I997a6dc9ab728e9e87df321c30d0a26ce2853698
Reviewed-on: https://gerrit.openafs.org/13108
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>