bug#2022: 23.0.60; Rmail buffer marked modified after saving it

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Cc: 2022@emacsbugs.donarmstrong.com
> Date: Sun, 25 Jan 2009 15:45:59 -0500
> 
> Eli Zaretskii wrote:
> 
> > The old (pre-mbox) Rmail also had the unseen attribute, but it never
> > marked the Rmail buffer modified when it was removed.
> 
> That's a good argument. I wonder how it worked...

By setting the buffer's modified flag, like it's done everywhere else.