option to disable validation under specified names

- added new 'validate-except' option, which configures an NTA with
  expiry of 0xffffffff.  NTAs with that value in the expiry field do not
  expire, are are not written out when saving the NTA table and are not
  dumped by rndc secroots

bin/tests/system/checkconf/good.conf

@@ -65,6 +65,9 @@ options {
 	max-cache-size 20000000000000;
 	nta-lifetime 604800;
 	nta-recheck 604800;
+	validate-except {
+		"corp";
+	};
 	transfer-source 0.0.0.0 dscp 63;
 	zone-statistics none;
 };