auth: Relocate NetRestrict support functions

Pull the NetRestrict and NetInfo support functions out of libutil,
and into libauth. This starts to concentrate all of our configuration
file parsing functions into the same place.

It also gets rid of a circular dependency. NetRestrict parsing relies
on functions from rx, so with this in libutil, we had the dependency
chain util->rx->util

Reviewed-on: http://gerrit.openafs.org/8027
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 1e76c59ea52b35f4d478fdbe85456160b1e9f8ec)

Change-Id: I7f886539e047ac84c02870ffb2d0ea37fb557026
Reviewed-on: http://gerrit.openafs.org/10036
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>