For a method called without argument, Js.wrap_meth_callback now adds an argument undefined
For a method called without argument, Js.wrap_meth_callback now adds an argument undefined

We used to add an argument 0 to a method called without argument. It
seems better to use undefined instead (as does Js.wrap_callback).

OCamlPro-Henry/js_of_ocaml,OCamlPro-Henry/js_of_ocaml,alainfrisch/js_of_ocaml,alainfrisch/js_of_ocaml,OCamlPro-Henry/js_of_ocaml,alainfrisch/js_of_ocaml,OCamlPro-Henry/js_of_ocaml,OCamlPro-Henry/js_of_ocaml,alainfrisch/js_of_ocaml,alainfrisch/js_of_ocaml