altos/scheme: (define (foo . bar)) has a pair, not list as card

altos/scheme: (define (foo . bar)) has a pair, not list as card

When defining a lambda with varargs, the args are not a list as the
final element is not a pair or nil. Use pair? instead of list? to
detect this form correctly.

Signed-off-by: Keith Packard <keithp@keithp.com>