hints_next_root
int hints_next_root(struct iter_hints* hints, uint16_t* qclass, int nolock);
r1 = hints_next_root(hints, &c1, nolock);
int hints_next_root(struct iter_hints* hints, uint16_t* qclass, int nolock);
r1 = hints_next_root(hints, &c1, nolock);