IP routing table is a tree of `IPRange`

to search one of them on the longest
match base. It is a kind of TRIE with one
way branching removed. Both IPv4 and IPv6
are supported.

For more information, see: http://www.mew.org/~kazu/proj/iproute/

- class Addr a => Routable a where
- data IPRTable k a
- empty :: Routable k => IPRTable k a
- insert :: Routable k => AddrRange k -> a -> IPRTable k a -> IPRTable k a
- delete :: Routable k => AddrRange k -> IPRTable k a -> IPRTable k a
- lookup :: Routable k => AddrRange k -> IPRTable k a -> Maybe a
- fromList :: Routable k => [(AddrRange k, a)] -> IPRTable k a
- toList :: Routable k => IPRTable k a -> [(AddrRange k, a)]