- Test changing case in different types and even adding a duplicate
  record that differs only in lettercase in RDATA.
- Also, test changing case in NSEC's next domain name. Should result
  in resign, but that doesn't happen right now.

- Semantic check: missing conversion of next NSEC to lowercase
  when comparing with apex.
- Changed condition when SERVFAIL is returned (no combination
  with any possible Ext RCODE).

Conflicts:
	Knot.files

Only RFC 4034 types are converted to lowercase.
Unified the conversion to one RRSet function used in both zone
parsing and packet parsing.

See merge request !287

 - needed because of master -> slave role switch