Implement a fast presix-set lookup. This magic trie is able to match a

Implement a fast presix-set lookup. This magic trie is able to match a
prefix addr/plen to a prefix-set spec addr/plen prefixlen min - max (a
prefix including prefixlen range). Every addr/plen pair is a node in the
trie and the prefixlen is added as a bitmask to those nodes.
For the lookup the any match is OK, there is no need to do longest or
best prefix matching.
Inspiration for this solution comes from the way bird implements this
which was done by Ondrej Zajicek santiago (at) crfreenet.org
OK benno@