bug#42039: 27.0.91; (posn-x-y (posn-at-point)) inconsistent with display-line-numbers-mode

[Eli Zaretskii]

> Cc: 42039@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Fri, 26 Jun 2020 15:55:31 +0300
> 
> > Your wish has been granted: this should now be fixed on the emacs-27
> > branch.
> 
> Thank you.
> 
> It's working fine now in the cases I really care about (so we can close 
> the report), but here's one you seem to have missed:
> 
> 1. M-x report-emacs-bug.
> 2. Toggle display-line-numbers-mode on.
> 3. Move point to the second display string ("If Emacs crashed...").
> 4. Evaluate (posn-x-y (posn-at-point)).

It worked in a previous version of the fix, but then I decided to be
over-cautious...

Fixed.