fixes #71; sorry about the polling implementation

tests/threads/trecursive_actor.nim

@@ -0,0 +1,19 @@
+discard """
+  outputsub: "0"
+"""
+
+import actors
+
+var
+  a: TActorPool[int, void]
+createActorPool(a)
+
+proc task(i: int) {.thread.} =
+  echo i
+  if i != 0: a.spawn (i-1, task)
+
+# count from 9 till 0 and check 0 is somewhere in the output
+a.spawn(9, task)
+a.join()
+
+