add test to ActorModelSpec

dispatcherShouldHandleQueueingFromMultipleThreads tests for possible race
conditions in prohibiting multiple threads running the same actor concurrently

akka-testkit/src/test/scala/akka/testkit/CallingThreadDispatcherModelSpec.scala

@@ -0,0 +1,11 @@
+package akka.testkit
+
+import akka.actor.dispatch.ActorModelSpec
+
+class CallingThreadDispatcherModelSpec extends ActorModelSpec {
+  import ActorModelSpec._
+  def newInterceptedDispatcher = new CallingThreadDispatcher with MessageDispatcherInterceptor
+  override def dispatcherShouldProcessMessagesInParallel {}
+}
+
+// vim: set ts=4 sw=4 et: