changed type names in QP trie code to match the usual convention:
 - qp_node_t -> dns_qpnode_t
 - qp_ref_t -> dns_qpref_t
 - qp_shift_t -> dns_qpshift_t
 - qp_weight_t -> dns_qpweight_t
 - qp_chunk_t -> dns_qpchunk_t
 - qp_cell_t -> dns_qpcell_t