Manage routes via a radix tree

[axeld]

Right now, the routes are not sorted at all; the in-order counts. As a temporary measurement, we could change this so that the routes are ordered by the completeness of their networking mask.

The optimal solution should implement a radix tree to look up the routes. The stack already contains the BSD radix source, but since that one is of poor code quality (but it works), a new and clean implementation would actually be preferred.