CCInt64(chore): conditionally define function existing in newer OCaml

src/core/CCInt64.ml

@@ -2,8 +2,13 @@
 
 include Int64
 
+[@@@iflt 4.13]
+
 let min : t -> t -> t = Stdlib.min
 let max : t -> t -> t = Stdlib.max
+
+[@@@endif]
+
 let sign i = compare i zero
 
 (* use FNV:

src/core/CCInt64.mli

@@ -18,6 +18,8 @@ include module type of struct
   include Int64
 end
 
+[@@@iflt 4.13]
+
 val min : t -> t -> t
 (** [min x y] returns the minimum of the two integers [x] and [y].
     @since 3.0 *)
@@ -26,10 +28,15 @@ val max : t -> t -> t
 (** [max x y] returns the maximum of the two integers [x] and [y].
     @since 3.0 *)
 
+[@@@endif]
+[@@@iflt 5.1]
+
 val hash : t -> int
 (** [hash x] computes the hash of [x], a non-negative integer.
     Uses FNV since 3.10 *)
 
+[@@@endif]
+
 val hash_to_int64 : t -> t
 (** Like {!hash} but does not truncate.
     Uses FNV.