Hello!

As a follow-up to this thread, attached is `nnregistry', a dumb back-end
whose sole purpose is to allow `gnus-summary-refer-parent-article' and
similar functions to work across back-ends.  It can be used like this:

--8<---------------cut here---------------start------------->8---
(setq gnus-refer-article-method
      '(current
	(nnregistry)
	(nnweb "gmane" (nnweb-type gmane))))
--8<---------------cut here---------------end--------------->8---

What do you think of the approach and code?

It's my first time hacking Gnus so I'd appreciate reviews.

Thanks,
Ludo'.

PS: I don't (yet) have a copyright assignment on file for Emacs.