reducing headers in gnus-summary-mail-forward ARG 4

[Ted Stern <stern+gnus@cray.com>]

I'm wondering how to reduce the number of headers in the ARG 4 option to
gnus-summary-mail-forward but not in any of the other options.

Changing message-forward-ignored-headers is not satisfactory -- this changes
the number of headers in the nil option but not the ARG 4 option.

,----[ gnus-summary-mail-forward documentation ]
| C-c C-f runs the command gnus-summary-mail-forward
|    which is an interactive compiled Lisp function in `gnus-msg'.
| (gnus-summary-mail-forward &optional ARG POST)
| 
| Forward the current message(s) to another user.
| If process marks exist, forward all marked messages;
| if ARG is nil, see `message-forward-as-mime' and `message-forward-show-mml';
| if ARG is 1, decode the message and forward directly inline;
| if ARG is 2, forward message as an rfc822 MIME section;
| if ARG is 3, decode message and forward as an rfc822 MIME section;
| if ARG is 4, forward message directly inline;
| otherwise, use flipped `message-forward-as-mime'.
| If POST, post instead of mail.
| For the `inline' alternatives, also see the variable
| `message-forward-ignored-headers'.
`----

-- 
 Ted Stern                                 Applications Group
 Cray Inc.                               office: 206-701-2182
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 Frango ut patefaciam -- I break that I may reveal
 (The Paleontological Society motto, equally apropos for debugging)