newRPL - Updated to build 1510 [official build remains at 1487]

[The Shadow]

Been quite a while since I've stopped by, when I get some time I should try NewRPL on a Prime!

I like what I'm seeing with the new loop structures and CKARG. As long as we're meddling, how feasible would these changes be?

* Allowing negative numbers for list slots. -1 being the last element, -2 being the second to last, etc. (Unfortunately there probably shouldn't be a slot 0 for fear of confusing POS and other commands.)

* Allowing a list as the first input for a FOR loop. The second input specifies where in the list to start, and the FOR variable reads out of the list thereafter, with STEP skipping entries as desired. The loop ends when STEP (or NEXT) produces a value that doesn't correspond to a list slot.

If altering FOR is not in the cards, perhaps a new loop FORLIST?