refs #277,#273

Conflicts:
	src/zone/zone-load.c

- If the found zone was last in canonical order and the QNAME
  was greater than the zone name, it returned the zone no matter
  if the QNAME belonged to the zone.
- Quick fix, would require more thorough testing and maybe complete
  change of the structure in which the zones are kept.

Closes #252

Refs #252

- define macro USE_HASH_TABLE in to enable the hash table

- Wrong values in character table for dnslib_tolower()
- zonec not including dnslib/debug.h

- Was trying to free the hashtable even if there was none.

closes #253

refs #5

- The function now deallocates all dnames, even those that have
  'node' field set, if told to (new parameter free_all_dnames).
- Changed all calls to this function (would need some thorough
  testing).
- This fixed last leak from nameserver.

refs #5

- Added the place to the preallocated space => reusable
  (no two threads should call to_wire() on one response).
- Also fixed leak from allocating the place for owner wire format.

refs #5

Conflicts:
	src/dnslib/zone.h