avoid clash with function called "x";

--- a/src/HOL/Tools/Function/partial_function.ML	Sun Apr 17 22:38:50 2016 +0200
+++ b/src/HOL/Tools/Function/partial_function.ML	Mon Apr 18 11:02:07 2016 +0200
@@ -246,7 +246,7 @@
     val tupleT = foldl1 HOLogic.mk_prodT aTs;
     val fT_uc = tupleT :: bTs ---> body_type fT;
     val f_uc = Var ((f_bname, 0), fT_uc);
-    val x_uc = Var (("x", 0), tupleT);
+    val x_uc = Var (("x", 1), tupleT);
     val uncurry = lambda head (uncurry_n arity head);
     val curry = lambda f_uc (curry_n arity f_uc);