move ask machinery from ActorRefProvider to pattern.AskSupport

- now everything is assembled in one spot
- also moved PromiseActorRef and AskTimeoutException from akka.actor
- plus a little boy-scouting

akka-remote/src/test/scala/akka/remote/RemoteCommunicationSpec.scala

@@ -83,8 +83,8 @@ akka {
 
     "support ask" in {
       Await.result(here ? "ping", timeout.duration) match {
-        case ("pong", s: PromiseActorRef) ⇒ // good
-        case m                            ⇒ fail(m + " was not (pong, AskActorRef)")
+        case ("pong", s: akka.pattern.AskSupport.PromiseActorRef) ⇒ // good
+        case m ⇒ fail(m + " was not (pong, AskActorRef)")
       }
     }