pywdns: add *_to_str() wrappers for opcode, rcode, rrclass, rrtype
pywdns: add *_to_str() wrappers for opcode, rcode, rrclass, rrtype

d4s/wdns,hstern/wdns,d4s/wdns,d4s/wdns,hstern/wdns,hstern/wdns,hstern/wdns