roken: configure checks for inet_ntop and inet_pton

Change-Id: Idf2eee040235bbf1f34ed993c74dd5936ae063c6
Reviewed-on: http://gerrit.openafs.org/11584
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: D Brashear <shadow@your-file-system.com>