no multithreading for actor update

Former-commit-id: aa575fabff183802cd326b24d5788bd44adbad95
Former-commit-id: a0d2b650aa5d3f19717049b17284eb76c694b24b

src/net/torvald/terrarum/Game.kt

@@ -349,8 +349,7 @@ constructor() : BasicGameState() {
                 i-- // array removed 1 elem, so also decrement counter by 1
             }
             else {
-                //actorContainer[i].update(gc, delta)
-                actorContainer[i].start()
+                actorContainer[i].update(gc, delta)
             }
             i++
         }

src/net/torvald/terrarum/gameactors/Actor.kt

@@ -9,14 +9,7 @@ import org.newdawn.slick.GameContainer
  */
 abstract class Actor : Comparable<Actor>, Runnable {
 
-    abstract protected fun update(gc: GameContainer, delta_t: Int) // use start() for multithreaded env
-
-    protected var thread: Thread? = null
-
-    fun start() {
-        thread = Thread(this, "ID: $referenceID")
-        thread!!.run()
-    }
+    abstract fun update(gc: GameContainer, delta_t: Int)
 
     /**
      * Valid RefID is equal to or greater than 32768.