bug#27427: 26.0.50; Native line numbers lead to display error in company-mode popup

[Eli Zaretskii]

> Cc: alexanderm@web.de, 27427@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Sun, 25 Jun 2017 19:24:21 +0300
> 
> Weren't menus in the terminal rendered using a certain special method, 
> different from overlays?

Yes.  We simply overwrite the glyph matrices with the menu contents,
and then force a screen update.

But this cannot work for features that want Emacs to return to the
main loop, because anything that triggers any kind of redisplay will
restore portions of the display from buffer text and mess up the menu.