split screen c-x o errs on negative arg

[David Chapman <Zvona at MIT-OZ>]

In Release 5.0 [Beta Test rev 7], FEP 18, on Lisp Machine Apiary-8 (3600):

This is with three buffer windows.  c- - c-x o.  I expected that to go
in the opposite direction around the set of windows from c-x o.

Say, the documentation for c-x o talks about ``the'' other window.  I
use three moderately often.

>>Error: The argument N to NTH, -1, was of the wrong type.
         The function expected a non-negative integer.
While in the function NTH  ZWEI:OTHER-WINDOW  ZWEI:COM-OTHER-WINDOW

NTH:  (P.C. = 26)
   Arg 0 (N): -1
   Arg 1 (OBJECT): (#<WINDOW 4013414> #<WINDOW 75425377> #<WINDOW 5552537>)
   Local 2 (N): SI:N
   Local 3 (OBJECT): -1

ZWEI:OTHER-WINDOW:  (P.C. = 37)
   Arg 0 (N): -1

ZWEI:COM-OTHER-WINDOW:  (P.C. = 5)