Unable to refer to some elements in unapplied functors

[jonludlam]

For example:

module X : functor ( Y : sig type t end ) -> sig
	module Z = Y
end

(** {!X.Z.t} *)

[Julow]

Note this currently resolves:

module X : functor ( Y : sig type t end ) -> sig
  type t = Y.t
end

(** {!X.t} *)