avoid infinite recursion in peephole optimizer function -- this had a debilitating effect on rationals and reals

--- a/NEWS	Mon Nov 07 22:21:57 2011 +0100
+++ b/NEWS	Mon Nov 07 22:22:01 2011 +0100
@@ -76,6 +76,11 @@
 a list and a nat.
 
 
+* Nitpick:
+  - Fixed infinite loop caused by the 'peephole_optim' option and affecting
+    'rat' and 'real'.
+
+
 *** FOL ***
 
 * New "case_product" attribute (see HOL).

--- a/src/HOL/Tools/Nitpick/nitpick_peephole.ML	Mon Nov 07 22:21:57 2011 +0100
+++ b/src/HOL/Tools/Nitpick/nitpick_peephole.ML	Mon Nov 07 22:22:01 2011 +0100
@@ -358,8 +358,6 @@
       (case (r1, r2) of
          (Join (r11, Rel x), _) =>
          if x = not3_rel then s_rel_eq r11 (s_not3 r2) else raise SAME ()
-       | (_, Join (r21, Rel x)) =>
-         if x = not3_rel then s_rel_eq r21 (s_not3 r1) else raise SAME ()
        | (RelIf (f, r11, r12), _) =>
          if inline_rel_expr r2 then
            s_formula_if f (s_rel_eq r11 r2) (s_rel_eq r12 r2)