Stdlib: add Option.try_with

lib_stdlib/option.ml

@@ -32,3 +32,5 @@ let first_some a b = match a, b with
   | None, Some v -> Some v
   | Some v, _ -> Some v
 
+let try_with f =
+  try Some (f ()) with _ -> None

lib_stdlib/option.mli

@@ -25,3 +25,5 @@ val unopt_map: f:('a -> 'b) -> default:'b -> 'a option -> 'b
 (** First input of form [Some x], or [None] if none **)
 val first_some: 'a option -> 'a option -> 'a option
 
+(** [Some (f ())] if [f] does not raise, [None] otherwise *)
+val try_with : (unit -> 'a) -> 'a option