WAITTASK expression

   Synopsis:
      Starts an Axmud task and waits for it to terminate

   Notes:
      Starts a new Axmud task. The script waits until the new task has 
         terminated, before resuming execution.
      The expression is the name of the new task. It can be a task label (e.g.
         "stat", "status") or its formal name (e.g. "status_task").
         
   Examples:
      WAITTASK "advance"
      PRINT "I'm back, baby!"
