(calculator-radix-grouping-mode)

(calculator-radix-grouping-mode)
(calculator-radix-grouping-digits)
(calculator-radix-grouping-separator):
New defcustoms for the new radix grouping mode functionality.
(calculator-mode-hook): Now used in electric mode too.
(calculator-mode-map): Some new keys.
(calculator-message): New function.  Some new calls.
(calculator-string-to-number): New function,
(calculator-curnum-value): Use it.
(calculator-rotate-displayer, calculator-rotate-displayer-back)
(calculator-displayer-prev, calculator-displayer-next):
Change digit group size when in radix mode.
(calculator-number-to-string): Renamed from calculator-num-to-string.
Now deals with digit grouping in radix mode.