add test for “unorderly” shutdown of ActorSystem by PoisonPill

- uncovered nasty endless loop bug wrt. dead letters and a dead listener
- fixing that bug removed the MainBusReaper (sigh)
- also fix compilation of tutorial-first, but that REALLY needs to be
  changed not to create RoutedActorRef using new!

akka-remote/src/main/scala/akka/remote/RemoteActorRefProvider.scala

@@ -176,7 +176,7 @@ class RemoteActorRefProvider(
    * Copied from LocalActorRefProvider...
    */
   // FIXME: implement supervision, ticket #1408
-  def actorOf(system: ActorSystem, props: RoutedProps, supervisor: ActorRef, name: String): InternalActorRef = {
+  def actorOf(system: ActorSystem, props: RoutedProps, supervisor: InternalActorRef, name: String): InternalActorRef = {
     if (props.connectionManager.isEmpty) throw new ConfigurationException("RoutedProps used for creating actor [" + name + "] has zero connections configured; can't create a router")
     new RoutedActorRef(system, props, supervisor, name)
   }