More thoroughly mark Lwt_sequence deprecated

Lwt.add_task_l and Lwt.add_task_r are also deprecated by this.

Part of #361.

src/core/lwt.mli

@@ -1622,6 +1622,9 @@ val waiter_of_wakener : 'a u -> 'a t
 (** {3 Linked lists of promises} *)
 
 val add_task_r : ('a u) Lwt_sequence.t -> 'a t
+  [@@ocaml.deprecated
+" Deprecated because Lwt_sequence is an implementation detail of Lwt. See
+  https://github.com/ocsigen/lwt/issues/361"]
 (** [Lwt.add_task_r sequence] is equivalent to
 
 {[
@@ -1638,6 +1641,9 @@ p
       optimization, which may be removed. *)
 
 val add_task_l : ('a u) Lwt_sequence.t -> 'a t
+  [@@ocaml.deprecated
+" Deprecated because Lwt_sequence is an implementation detail of Lwt. See
+  https://github.com/ocsigen/lwt/issues/361"]
 (** Like {!Lwt.add_task_r}, but the equivalent code calls {!Lwt_sequence.add_l}
     instead. *)
 

src/core/lwt_sequence.mli

@@ -34,6 +34,10 @@
    doubly-linked list library as an alternative.
 *)
 
+[@@@ocaml.deprecated
+" This module is an implementation detail of Lwt. See
+   https://github.com/ocsigen/lwt/issues/361"]
+
 type 'a t
   (** Type of a sequence holding values of type ['a] *)