Lwt_react: use physical equality internally to implement S.l[2-6]_s

This avoids a failure when some inputs cannot be compared (if they
contain functional values, for instance).
We need to do something anyway if one of the inputs changes, so it makes
sense to use physical equality here.

src/react/lwt_react.cppo.ml

@@ -455,19 +455,19 @@ module S = struct
     map_s ?eq f s1
 
   let l2_s ?eq f s1 s2 =
-    map_s ?eq (fun (x1, x2) -> f x1 x2) (l2 (fun x1 x2 -> (x1, x2)) s1 s2)
+    map_s ?eq (fun (x1, x2) -> f x1 x2) (l2 ~eq:(==) (fun x1 x2 -> (x1, x2)) s1 s2)
 
   let l3_s ?eq f s1 s2 s3 =
-    map_s ?eq (fun (x1, x2, x3) -> f x1 x2 x3) (l3 (fun x1 x2 x3-> (x1, x2, x3)) s1 s2 s3)
+    map_s ?eq (fun (x1, x2, x3) -> f x1 x2 x3) (l3 ~eq:(==) (fun x1 x2 x3-> (x1, x2, x3)) s1 s2 s3)
 
   let l4_s ?eq f s1 s2 s3 s4 =
-    map_s ?eq (fun (x1, x2, x3, x4) -> f x1 x2 x3 x4) (l4 (fun x1 x2 x3 x4-> (x1, x2, x3, x4)) s1 s2 s3 s4)
+    map_s ?eq (fun (x1, x2, x3, x4) -> f x1 x2 x3 x4) (l4 ~eq:(==) (fun x1 x2 x3 x4-> (x1, x2, x3, x4)) s1 s2 s3 s4)
 
   let l5_s ?eq f s1 s2 s3 s4 s5 =
-    map_s ?eq (fun (x1, x2, x3, x4, x5) -> f x1 x2 x3 x4 x5) (l5 (fun x1 x2 x3 x4 x5-> (x1, x2, x3, x4, x5)) s1 s2 s3 s4 s5)
+    map_s ?eq (fun (x1, x2, x3, x4, x5) -> f x1 x2 x3 x4 x5) (l5 ~eq:(==) (fun x1 x2 x3 x4 x5-> (x1, x2, x3, x4, x5)) s1 s2 s3 s4 s5)
 
   let l6_s ?eq f s1 s2 s3 s4 s5 s6 =
-    map_s ?eq (fun (x1, x2, x3, x4, x5, x6) -> f x1 x2 x3 x4 x5 x6) (l6 (fun x1 x2 x3 x4 x5 x6-> (x1, x2, x3, x4, x5, x6)) s1 s2 s3 s4 s5 s6)
+    map_s ?eq (fun (x1, x2, x3, x4, x5, x6) -> f x1 x2 x3 x4 x5 x6) (l6 ~eq:(==) (fun x1 x2 x3 x4 x5 x6-> (x1, x2, x3, x4, x5, x6)) s1 s2 s3 s4 s5 s6)
 
   (* +---------------------------------------------------------------+
      | Monadic interface                                             |