Fix bug #13720 with auto-save-timeout less than 4 seconds.

 src/keyboard.c (read_char): Fix calculation of auto-save time out
 when auto-save-timeout is less than 4.

src/ChangeLog

 2013-02-15  Eli Zaretskii  <eliz@gnu.org>
 
+	* keyboard.c (read_char): Fix calculation of auto-save time out
+	when auto-save-timeout is less than 4.  (Bug#13720)
+
 	* w32proc.c (new_child): Free up to 2 slots of dead processes at a
 	time.  Improve diagnostics in DebPrint.
 	(reader_thread): If cp->char_avail is NULL, set the FILE_AT_EOF

src/keyboard.c

@@ -2657,9 +2657,10 @@ read_char (int commandflag, Lisp_Object map,
 	  && XINT (Vauto_save_timeout) > 0)
 	{
 	  Lisp_Object tem0;
-	  EMACS_INT timeout = (delay_level
-			       * min (XFASTINT (Vauto_save_timeout) / 4,
-				      MOST_POSITIVE_FIXNUM / delay_level));
+	  EMACS_INT timeout = XFASTINT (Vauto_save_timeout);
+
+	  timeout = min (timeout, MOST_POSITIVE_FIXNUM / delay_level * 4);
+	  timeout = delay_level * timeout / 4;
 	  save_getcjmp (save_jump);
 	  restore_getcjmp (local_getcjmp);
 	  tem0 = sit_for (make_number (timeout), 1, 1);