(arith-progo start step len result): result is the list
(start, start+step, ..., start+(len-1)*step). Length 0 yields the
empty list. Negative steps and zero step are supported.
Useful for FD-style domain construction:
(arith-progo 1 1 9 dom) -> (1 2 3 4 5 6 7 8 9)
6 new tests, 538/538 cumulative.
