Update from version 1.4.0nb1 to 1.5.1.

OK'ed by wiz@

Pkgsrc changes:
o Explicitly mark dependency on openssl >= 0.9.7, should fix PR#41633

Upstream changes:

1.5.1
Example tools:
* ldns-signzone was broken in 1.5.0 for multiple keys, this
          has been repaired

Build system:
        * Removed a small erroneous output warning in
          examples/configure and drill/configure

1.5.0
Bug fixes:
* fixed a possible memory overflow in the RR parser
* build flag fix for Sun Studio
* fixed a building race condition in the copying of header
  files
* EDNS0 extended rcode; the correct assembled code number
  is now printed (still in the EDNS0 field, though)
* ldns_pkt_rr no longer leaks memory (in fact, it no longer
  copies anything all)

API addition:
* ldns_key now has support for 'external' data, in which
  case the OpenSSL EVP structures are not used;
  ldns_key_set_external_key() and ldns_key_external_key()
* added ldns_key_get_file_base_name() which creates a
  'default' filename base string for key storage, of the
  form "K<zone>+<algorithm>+<keytag>"
* the ldns_dnssec_* family of structures now have deep_free()
  functions, which also free the ldns_rr's contained in them
* there is now an ldns_match_wildcard() function, which checks
  whether a domain name matches a wildcard name
* ldns_sign_public has been split up; this resulted in the
  addition of ldns_create_empty_rrsig() and
  ldns_sign_public_buffer()

Examples:
* ldns-signzone can now automatically add DNSKEY records when
  using an OpenSSL engine, as it already did when using key
  files
* added new example tool: ldns-nsec3-hash
* ldns-dpa can now filter on specific query name and types
* ldnsd has fixes for the zone name, a fix for the return
          value of recvfrom(), and an memory initialization fix
          (Thanks to Colm MacC叩rthaigh for the patch)
        * Fixed memory leaks in ldnsd

1.4.1
Bug fixes:
* fixed a build issue where ldns lib existence was done too early
* removed unnecessary check for pcap.h
* NSEC3 optout flag now correctly printed in string output
* inttypes.h moved to configured inclusion
* fixed NSEC3 type bitmaps for empty nonterminals and unsigned
  delegations

API addition:
* for that last fix, we added a new function
  ldns_dname_add_from() that can clone parts of a dname

(he)