(calc-do-keypad): Use it.
(calc-keypad-map): Move into `calc-keypad-mode'.
Change all toplevel `setq' forms to `defvar' forms, and move them
before their first use. Use `when', `unless'. Remove trailing
periods from error forms. Add description and headers suggested by
Emacs Lisp coding conventions.
(calc-do-keypad): Don't attempt to use nonexistent global
mouse-map, use calc-keypad-map.
(calc-keypad-x-left-click): Renamed to calc-keypad-left-click.
(calc-keypad-left-click): Don't use mouse-map; update to new event
interface.
(calc-keypad-x-middle-click, calc-keypad-x-right-click): Ditto.
(calc-keypad-press): Use `unread-command-events' instead of
`unread-command-char'.
