zonedb - wrong lookup of root zone submatches

Problem

Fails to find root zone by subdomain because of knot_dname_lf doesn't always put \x00 to the beginning of the zone, therefore root zone is not a prefix of every name.

Solution

I rewrote the zonedb anyway to not use longest prefix match in trie. This is because if name suffix is in a hashtable node, it will trie to find suffix by cutting characters from the beginning of the name, while it could cut whole labels instead.