Add refer checking to xmlrpc.cgi, while still allowing direct access

xmlrpc.cgi

@@ -20,7 +20,7 @@ use WebminCore;
 use POSIX;
 use Socket;
 $force_lang = $default_lang;
-$trust_unknown_referers = 1;
+$trust_unknown_referers = 2;	# Only trust if referer was not set
 &init_config();
 $main::error_must_die = 1;