move listen-on correctness checks into check.c

errors in listen-on and listen-on-v6 can now be detected
by named-checkconf.

bin/tests/system/checkconf/bad-doh-2.conf

@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+tls local-tls {
+	key-file "key.pem";
+	cert-file "cert.pem";
+};
+
+# undefined 'http' specification
+options {
+	listen-on port 8080 http unknown tls local-tls { 10.53.0.1; };
+};