--open not respected when resolving references in {!modules: ...} output

[jonludlam]

Given a file to_open.mli containing

module Foo : sig
end

and a file containing:

module X : sig
  (** {!Foo} {!To_open.Foo} *)
end

(** {!modules: X} *)

If the second is linked with --open To_open then both references in module X are resolved, but only the second is resolved when they appear in the output of the {!modules}.