New LookupIPRoute3 and adapted RadixIPLookup

[Eddie Kohler]

Hi Brecht, others,

Thanks for your IP-route-lookup elements! We've updated our elements along
the same lines. Please give them a try and let us know if there are any
problems.

      LinearIPLookup -- a linear list of routes; like old LookupIPRoute,
but adds an optimization so not every route need be checked; has dynamic
adding and deleting of routes

      StaticIPLookup -- LinearIPLookup minus dynamic adding/deleting

      SortedIPLookup -- LinearIPLookup plus a sorted routing table;
equivalent to your LookupIPRoute3; but LinearIPLookup might now be fast
enough

Eddie