add CCOpt.value to improve compat with Stdlib.Option

src/core/CCOpt.ml

@@ -106,6 +106,9 @@ let fold f acc o = match o with
 let get_or ~default x = match x with
   | None -> default
   | Some y -> y
+let value x ~default = match x with
+  | None -> default
+  | Some y -> y
 
 let get_exn = function
   | Some x -> x

src/core/CCOpt.mli

@@ -72,6 +72,10 @@ val get_or : default:'a -> 'a t -> 'a
     returns [default] if [o = None].
     @since 0.18 *)
 
+val value : 'a t -> default:'a -> 'a
+(** Similar to the stdlib's [Option.value] and to {!get_or}.
+    @since NEXT_RELEASE *)
+
 val get_exn : 'a t -> 'a
 (** Open the option, possibly failing if it is [None].
     @raise Invalid_argument if the option is [None]. *)