Recentering on scroll

[Chong Yidong]

Can anyone reproduce bug#873 (occasional recentering during C-n)?  I
thought I could reproduce it at some point, using the recipe given in
that bug report, but I can't seem to do it now.

> After setting this in .emacs:
>
> (setq scroll-preserve-screen-position 'always
>       scroll-conservatively           most-positive-fixnum ;; any large number
>       scroll-step                     0)
>
> scroll-down causes recentering. This is a regression.