Initial commit of DNS helper .js, intended to be used with the new load()

format for non-blocking DNS lookups.

exec/load/dnshelper.js

+/*
+   dnshelper.js -- quick script to do a DNS resolution and display the result.
+
+   This is intended to be used from inside another JS script by using the
+   Synchronet load() function. Example:
+
+   q = load(true,"dnshelper.js",some_ip_address);
+   var dns_result = 0;
+   while (!dns_result) {
+      dns_result = q.read();
+   }
+   log("Got result: " + dns_result);
+
+   This is intended for utilization in a situation where blocking is not
+   acceptable.  Otherwise simply use resolve_host() as per normal.
+*/
+
+if (!argv[0]) {
+	exit();
+}
+
+var resolved_hostname = resolve_host(argv[0]);
+
+if (resolved_hostname)
+	resolved_hostname;
+else
+	false;
+