Multiple consumers like ipfw, netflow or new route lookup algorithms
need to get the prefix data out of struct rtentry.
Instead of providing direct access to the rtentry, create IPv4/IPv6
accessors to abstract struct rtentry internals and avoid including
internal routing headers for external consumers.
While here, move struct route_nhop_data to the public header, so external
customers can actually use lookup functions returning rt&nhop data.
Differential Revision: https://reviews.freebsd.org/D27416
df9053920f