zmacs split screen; c-x o loses

[ZVONA@MIT-OZ]

        * with three windows, if you do c-3 c-x o, you end up with one window.
        c-2 c-x o doesn't.  I thought that a numeric argument of n was supposed
        to move you to the nth window.

    n is zero-based.  Right now it selects the fourth window that you
    cannot see, which ends up the whole size of the screen.
    Alternatively, it could be a no-op, or max'ed and select the
    furthest away, or be changed to 1-based.  I don't care.

It seems that the most consistent thing would be to barf on
out-of-range arguments, where an argument is out of range if it is
equal to or greater than the number of visible windows.  Note that if
this were extended consistently to the one-window-visible case, it
would barf if you did c-x o with no argument when there is only one
window visible.  I've argued for that before, actually.