uniform handling of interrupts

--- a/src/Pure/Isar/toplevel.ML	Tue Sep 20 10:36:33 2005 +0200
+++ b/src/Pure/Isar/toplevel.ML	Tue Sep 20 13:17:32 2005 +0200
@@ -646,7 +646,7 @@
   Poly/ML needs exception Interrupt to be handled. SML/NJ needs IO to be handled.*)
 fun get_interrupt src = SOME (Source.get_single src) 
                         handle Interrupt => NONE
-                             | IO.Io _ => get_interrupt src;
+                             | IO.Io _ => NONE;
 
 fun raw_loop src =
   (case get_interrupt (Source.set_prompt (prompt_state (get_state ())) src) of