test: update tests after internal api change

Commit 0aa1335 changes the way timeout events are dispatched. Update
two tests that still used the old way.

test/message/timeout_throw.out

@@ -3,4 +3,4 @@
   ^
 ReferenceError: undefined_reference_error_maker is not defined
     at null._onTimeout (*test*message*timeout_throw.js:*:*)
-    at Timer.listOnTimeout [as ontimeout] (timers.js:*:*)
+    at Timer.listOnTimeout (timers.js:*:*)

test/pummel/test-timer-wrap.js

@@ -24,12 +24,13 @@ var assert = require('assert');
 
 var timeouts = 0;
 var Timer = process.binding('timer_wrap').Timer;
+var kOnTimeout = Timer.kOnTimeout;
 
 var t = new Timer();
 
 t.start(1000, 0);
 
-t.ontimeout = function() {
+t[kOnTimeout] = function() {
   timeouts++;
   console.log('timeout');
   t.close();