bug#10024: 24.0.91; save-restriction fails to restore the screen

[martin rudalics]

> But save-excursion also does not restore the window. It restores point
> (etc.). If a redisplay happens inside save-excursion, the window can
> scroll.

It _could_ scroll back to the initial position when, returning from the
excursion, point is off-screen.  Chances are that even the window-start
position after that is the same as before the excursion.  But there's
_no_ guarantee.  So you should restore the old position using something
like either `recenter' or `set-window-start'.

martin