The prefix management code currently resides in nd6, leaving only the
unused router renumbering capability in the in6_prefix files. Removing
it will make it easier for us to provide locking for the remainder of
IPv6 by reducing the number of objects requiring synchronized access.
This functionality has also been removed from NetBSD and OpenBSD.
Submitted by: George Neville-Neil <gnn at neville-neil.com>
Discussed with/approved by: suz, keiichi at kame.net, core at kame.net