bug#25308: Shorten long "ui-lines" in Custom buffers

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Cc: Jonas Bernoulli <jonas@bernoul.li>,  25308@debbugs.gnu.org
> Date: Sun, 03 Nov 2019 14:13:05 +0100
> 
> Yes, it works on both text based and graphical displays.  Please see
> the attached patch.
> 
> Lars suggested to remove the lines entirely, but I think I prefer to
> not change that for now.  Perhaps it would make more sense as part of
> a bigger overhaul of the look and feel of customize.
> 
> Any comments?

If your patch works, I have no comments.