bug#25708: 25.1.91; Allow users to inhibit printing for 'emacsclient -c -t'

[Eli Zaretskii <eliz@gnu.org>]

> From: peder@klingenberg.no (Peder O. Klingenberg)
> Date: Sun, 19 Feb 2017 21:54:22 +0100
> Cc: 25708@debbugs.gnu.org
> 
> > It would be great if emacsclient had a way to inhibit printing the
> > result, for cases where the user is only eval'ing the expressions for
> > their side effects.
> 
> Emacsclient claims to have that functionality already.  From the
> usage-message:
> 
> -q, --quiet		Don't display messages on success
> 
> This should, in my opinion, cover the case of successfully eval-ing
> forms.  However, -q currently has no effect on output from emacs, it
> only inhibits messages about connecting to emacs.
> 
> The attached patch should prevent emacsclient from printing non-error
> output from emacs to the terminal.
> 
> With this the terminal stays quiet after exiting the client frame when I
> do "emacsclient -q -c -e '(+ 2 3)'".  Without the -q, the terminal
> prints 5 as before.

Thanks, but I think this warrants a separate command-line option, or
maybe a special argument to --quiet.  Otherwise, it would be an
incompatible change in behavior.