Update copyright.

Update copyright.
(timeclock-ask-before-exiting): Put `timeclock-query-out' on
`kill-emacs-query-functions' rather than `kill-emacs-hook'.
(timeclock-mode-string): Doc fix.
(timeclock-modeline-display): Doc fix.  Use `global-mode-string' rather
than `mode-line-format'.
(timeclock-query-out): Doc fix.
(timeclock-update-modeline): No need for `let*', so use `let'.
Add some help-echo text to `timeclock-mode-string'.
(timeclock-mode-string): Give it the risky-local-variable property,
so that help-echo text will display.
(timeclock-find-discrep): Set `accum' to 0 if `timeclock-discrepancy' is nil.