P2p: Fix Hashtbl for PeerRing

Export hash in INTERNAL_HASH. now Peer_id.Id is hashable

src/lib_crypto/s.ml

@@ -95,6 +95,8 @@ module type INDEXES = sig
 
   type t
 
+  val hash : t -> int
+
   val to_path: t -> string list -> string list
   val of_path: string list -> t option
   val of_path_exn: string list -> t

src/lib_p2p/p2p_acl.ml

@@ -9,7 +9,6 @@
 
 module PeerRing = Ring.MakeTable(struct
     include P2p_peer.Id
-    let hash = Hashtbl.hash
   end)
 
 module PatriciaTree(V:HashPtree.Value) = struct