Stepper protocol

[Eric Dean Tribble <tribble>]

MarkM also suggested having value() return NULL when the Stepper has
no more values.  I rather like that, except that we can't write the
Samlltalk equivalent:

[tableStepper value] whileTrue: [something.  tableStepper value].

I can imagine making the translator recognize the condition  'x = nil'
and converting it to just 'x' (that'd be nice).

Having a NULL return encourages me to use 'fetch' and 'get' (for NULL
return vs error) instead of value.  any reactions?

dean