less offensive terminology

--- a/src/HOL/Tools/Sledgehammer/async_manager.ML	Fri Nov 18 11:47:12 2011 +0100
+++ b/src/HOL/Tools/Sledgehammer/async_manager.ML	Fri Nov 18 11:47:12 2011 +0100
@@ -203,7 +203,7 @@
       val state' = make_state manager timeout_heap [] (killing @ canceling) messages store;
       val _ =
         if null killing then ()
-        else Output.urgent_message ("Killed active " ^ das_wort_worker ^ "s.")
+        else Output.urgent_message ("Interrupted active " ^ das_wort_worker ^ "s.")
     in state' end);