Module descriptions should not appear in includes

[lpw25]

When a module has a description comment:

(** This is the module that does foos *)
module Foo = struct
  val x : int
  ...
end

it gets included in the documentation of includes of that module:

include Foo

This is the module that does foos

val x : int

It probably shouldn't be since the comment describes the module itself rather than its contents, and if someone wants to know about Foo itself they can just follow the link and read about it.