fixed OCaml driver

added mach.int.Int
removed list.Length

drivers/ocaml-gen.drv

@@ -104,10 +104,6 @@ theory list.List
   syntax function Cons "(%1 :: %2)"
 end
 
-theory list.Length
-  syntax function length "(List.length %1)"
-end
-
 theory list.Mem
   syntax predicate mem "(List.mem %1 %2)"
 end
@@ -158,6 +154,11 @@ module array.Array
   syntax val blit          "Why3__Array.blit"
 end
 
+module mach.int.Int
+  syntax val ( / ) "Why3__BigInt.computer_div"
+  syntax val ( % ) "Why3__BigInt.computer_mod"
+end
+
 module mach.int.Int31
   (* even on a 64-bit machine, it is safe to use type int for 31-bit integers *)
   syntax val       of_int   "Why3__BigInt.to_int"