bug#56393: Actually fix the long lines display bug

[Eli Zaretskii]

> Date: Sat, 09 Jul 2022 11:09:40 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: gerd.moellmann@gmail.com, larsi@gnus.org, 56393@debbugs.gnu.org
> 
> >  emacs -Q
> >  C-x C-f src/xdisp.c RET
> >  M->
> >  C-u 37100 C-p
> >
> > This signals an error "Beginning of buffer".
> >
> 
> Nice.  That's a recipe you concocted knowing the implementation details, 
> didn't you?  😉

Of course ;-)

> > And if I use M-v instead of C-p, I don't get an error message, but I 
> > don't get to the line I wanted, either: it silently stops much earlier.
> >
> 
> This I cannot reproduce, I can scroll through the whole buffer with M-v 
> without any visible problems.  I tried to set the auto repeat rate to 50, 
> and still do not see any problems.

No, I meant this:

  C-u 37100 M-v