add link from Actor JavaDoc to UntypedActor

akka-actor/src/main/scala/akka/actor/Actor.scala

@@ -369,6 +369,8 @@ object Actor {
  * `context`. The only abstract method is `receive` which shall return the
  * initial behavior of the actor as a partial function (behavior can be changed
  * using `context.become` and `context.unbecome`).
+ * 
+ * This is the Scala API (hence the Scala code below), for the Java API see [[akka.actor.UntypedActor]].
  *
  * {{{
  * class ExampleActor extends Actor {