bug#16034: 24.3.50; scrolling is very long to happen or never happen

[Stefan Monnier]

> (with-selected-window (next-window) (scroll-up 12))

> This return nil as expected but the next window to the one handling
> "*scratch*" doesn't move, but wait a certain time (up to one minute or
> more sometimes) and the window finish to scroll.

I think I know what's going on.  It's probably due to my patch that adds
`redisplay' fields everywhere, and here it ends up not marking the
`next-window' for redisplay, for some reason.

Thanks for the good recipe, the patch should follow later today,


        Stefan