suggestion: ranges with step -1

[Joerg Arndt <arndt@jjj.de>]

We have the (neat) ranges now:

? v=[3,4,5]
[3, 4, 5]
? v[1..2]
[3, 4]

Would it be sensible to allow "backward" ones as well?

? v[2..1]
  ***   at top-level: v[2..1]
  ***                 ^-------
  *** _[_.._]: inconsistent dimensions in _[..].


(btw. I do not understand the error message)

Best regards,    jj