Fix: variables contraint to a value at declaration were buggy (close #2)

cf example/Bug/freevar.lut node ko

examples/Bug/freevar.lut

 -- ok works fine, but not ko:
 
  node ko () returns (b: int [0; 0]; a: int) = a = b 
- node ok () returns (a: int [0; 0]; b: int) = a = b 
\ No newline at end of file
+ node ok () returns (a: int [0; 0]; b: int) = a = b
+

lutin/src/ne.ml

@@ -106,8 +106,8 @@ let (substl_to_string : subst list -> string) =
   fun sl ->
     (List.fold_left
        (fun acc ((vn, a), ne) ->
-	  (acc ^ "   " ^ (Value.num_value_to_string a) ^ "." ^ vn ^
-	   " -> " ^ to_string ne ^ "\n")
+	       (acc ^ "   " ^ (Value.num_value_to_string a) ^ "." ^ vn ^
+	        " -> " ^ to_string ne ^ "\n")
        )
        ""
        sl
@@ -369,7 +369,7 @@ let (split : t -> split_res) =
     let divide c1 c2 = 
       match (c1,c2) with
         | I i1, I i2 -> Num.eq_num (Num.mod_num i2 i1) (Num.Int 0)
-        | _ ,_ -> true
+        | _, _ -> assert false (* used to be "true" instead, but it looked weird! *)
     in
     let cl =  (StringMap.fold (fun v c acc -> (c,v)::acc) ne []) in
     let res =