bug#22315: [patch][gnus] allow functions for checking mails

[Rasmus]

Hi,

I use my mydomain.net for all my private mails.  As such my set of mail
accounts is basically ".*@mydomain.net".  I reserve a couple of addresses
like foo@mydomain.net for the local foo club's mailing list, though.
Thus, foo@mydomain.net is not one of my emails.

Since Emacs doesn't have regexp look-ahead it's pretty difficult to bend
message-alternative-emails, message-dont-reply-to-names,
gnus-ignored-from-addresses to recognize the above rule.

The attached patches allow the three variables message-alternative-emails,
gnus-ignored-from-addresses and message-dont-reply-to-names to be
predicates.  Thus, I can solve my woes with this simple predicate:

    (defun rasmus/mailp (email)
      (let (case-fold-search)
      ;; rasmus/my-mails is known.
        (and (string-match-p rasmus/my-mails email)
             (not (string-match-p rasmus/ml-mails email)))))

Also, I don't know how changelog works for Gnus now (or whenever it moves
to emacs.git).  Also, I don’t know if the patch should be against gnus.git
or emacs.git.  The attached patches should work with the master branch of
gnus.git.

Thanks,
Rasmus

-- 
Tack, ni svenska vakttorn. Med plutonium tvingar vi dansken på knä!

0001-Allow-message-alternative-emails-to-be-a-function.patch
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0002-Allow-gnus-ignored-from-addresses-to-be-a-function.patch
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0003-Allow-message-dont-reply-to-names-to-be-a-function.patch
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