Out-of-zone data handling for [A,I]XFR, DDNS.

- Added an error handling function
- Changed some static functions a bit - they now return error codes
  instead of NULL

Refs #102
Added missing string reference to log message.

Refs #102
Delete changeset RR when it is out of zone.

Refs #102
Do not allow out-of-zone data for DDNS.

- RFC 2136 states that the server should return the 'NOTZONE' error
  code, which it is correcly doing now, so there's no need to change it.
- Minor change only, since the actual check is somewhere before this code
  executes, but I've left the new_node functions as it was, since we
  may wish to allow some malformations later.

Refs #102
/s/KNOT_EBADZONE/KNOT_EOUTOFZONE/g/

Refs #102
Remove deprecated descriptor item LITERAL
Fix some descriptors with respect to RFC 3597
Add descriptors for some obsolete records
Fixed mask calculation on big-endian platforms, cleaned up comparison.

refs #100
Use obsolete descriptors during dname parsing
Changed out-of-zone processing in XFR.

     - Inserting DNAMEs from out-of-zone RRs into tmp DNAME table messed
things up when we free'd the RRSet, it's better to check before
inserting into table (one could rollback the table, but there are some
corner cases not worth solving)

Refs #102
Small fix (faulty if)

Refs #102
Added a check for struct mmsghdr for some cases of missing headers.
Replaced htobe32() with htonl() as it's probably more correct.
Merge branch 'bigendian_acl_fix' of /git/repositories/knot
Fix dname leak
Nitpick in comment :)
Merge branch 'obsolete_records' of /git/repositories/knot
Removed duplicated code.

* xfrin_add_new_node and ddns_add_new_node were duplicates
  - knot_node_set_zone() was called in the _add functions anyway
* merged checks for NSEC3-related RR to knot_rrset_is_nsec3rel()
  - the empty RR check was pointless, as even if empty, the node
    shouldn't be searched in normal tree
rename xfrin_handle_error -> xfrin_log_error