add CCOpt.{some,none}

close #382

src/core/CCOpt.ml

@@ -37,6 +37,8 @@ let equal f o1 o2 = match o1, o2 with
   | Some x, Some y -> f x y
 
 let return x = Some x
+let some = return
+let none = None
 
 let[@inline] flat_map f o = match o with
   | None -> None

src/core/CCOpt.mli

@@ -34,6 +34,14 @@ val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
 val return : 'a -> 'a t
 (** [return x] is a monadic return, that is [return x = Some x]. *)
 
+val some : 'a -> 'a t
+(** Alias to {!return}.
+    @since NEXT_RELEASE *)
+
+val none : 'a t
+(** Alias to {!None}.
+    @since NEXT_RELEASE *)
+
 val (>|=) : 'a t -> ('a -> 'b) -> 'b t
 (** [o >|= f] is the infix version of {!map}. *)