copy message for Steppers

[Eric Dean Tribble <tribble>]

Opps.  Every Stepper must implement the copy message.  Remember
Steppers are supposed to be treated like variables.  Thus we should
almost never pass a pointer to a Stepper around (xLint??).  Instead,
pass a pointer to a copy.  MarkM observed that this let's us program
with promiscuous side-effects while maintaining a side-effect free
semantics!  

dean