Replace ldns_rbtree with getdns_rbtree

As much as possible.
In dnssec ldns_rbtree is inderectly used via the dnssec_zone struct

This change forces use to embed the data in the nodes as getdns_rbtree does not have a data attribute. This is good because lesser allocs and free's and thus slightly faster and less likely to leak memory.
fix: local_hosts set keys and shallow free returns
memory leak fixes (found with valgrind)