Zone adjusting (CNAMEs and glue RRs).

Zone database:
Added functions
 - zdb_adjust_cname() - saves pointer to the node where the CNAME
     record points.
 - zdb_adjust_delegation_point() - marks node as delegation point,
     processes all its 'children', marks them as non authoritative
     and extracts all glue records from them.
 - zdb_adjust_zone() - uses the previous two functions to adjust
     all nodes in the zone.
zdb_insert_name() modified to properly insert the node in its
  place.
zdb_add_zone() modified to adjust the zone after creating.
zdb_insert_nodes_into_zds() modified not to insert non
  authoritative nodes into the zone data structure.

Zone node:
New flag for zone node - 2 - if non-authoritative.
  (+ setter and getter)
Glue list is now ldns_rr_list.
zn_get_glue() changed to accept desired owner name.
Added zn_get_glues() to get all glue records from the node.
Added zn_push_glue() to add glue records to the node. The function
  also sorts the glue records on each call.

Nameserver:
Glue records adding slightly modified (inserting all glue RRs
  by default, should change in future).