bug#9520: 24.0.50; hide<->show feature of RMAIL's MIME handling is broken

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> cc: Eli Zaretskii <eliz@gnu.org>
> Date: Tue, 15 Nov 2011 21:47:49 -0500
> 
> 
> Bisected to this commit:
> 
> revno: 105643
> committer: Eli Zaretskii <eliz@gnu.org>
> branch nick: trunk
> timestamp: Sat 2011-09-03 11:44:16 +0300
> message:
>   Fix display by Rmail of bidirectional text in MIME email messages.
>   
>    lisp/mail/rmailmm.el (rmail-mime-insert-tagline): Insert an extra
>    newline before and after the tag line, so it doesn't interfere
>    with determining the paragraph direction of bidirectional text.

Yes, I guessed that much ;-)

Since the above adds 2 extra newlines, some other code should remove
them, or take them into consideration, but doesn't.  I will get to
that in a couple of days, unless you beat me to it.