[Kst] Advance one screen

[Brisset, Nicolas]

> if we do this, how does the user implement "read from f0 to 
> the end, to a maximum of N points".  This is not an uncommon 
> thing for us to want to do in real time mode (though 
> admitedly, we normally forget about the 'max points' 
> part, and end up filling up a lot of Ram after a day or so...)
How is possible now to specify you want to read from f0 to the end, to a
maximum of N points currently ? I don't see how this works...

However, limiting the amount of points kept in memory could be an
interesting option... But I think it requires a new option.

Nicolas