initialize dns_dbmethods, dns_sdbmethods and dns_rdatasetmethods using explicit struct member names, so we don't have to keep track of NULLs for unimplemented functions any longer.
initialize dns_dbmethods, dns_sdbmethods and dns_rdatasetmethods using explicit struct member names, so we don't have to keep track of NULLs for unimplemented functions any longer.