protocol callbacks for route insertion and deletion from the central table.
RIP should maintain its own per-protocol queue of existing routes, scan it
periodically and call rte_discard() for routes that have timed out.
protocols and don't send route/interface updates to them and when they come up,
we resend the whole route/interface tables privately.
Removed the "scan interface list after protocol start" work-around.
interface since it makes much trouble everywhere. Instead, we understand
secondary addresses as subinterfaces.
- In case interface addresses or basic flags change, we simply convert it
to a down/up sequence.
- Implemented the universal neighbour cache. (Just forget what did previous
includes say of neighbour caching, this one is brand new.)
