dns/dnsperf: Fix building with bind 9.12 and newer

Patches are partially based on ISC upstream commit
64fe6bbaf2019f444475dfbf744eb6ea4e619c19 the other
parts are mine.

PR: 232774
Reported by: leeb@ratnaling.org
Approved by: portmgr (blanket)
Obtained from: https://gitlab.isc.org/isc-projects/bind9/commit/64fe6bbaf2019f444475dfbf744eb6ea4e619c19