The 2004-06-19 fix for who and pinky was incomplete, as ctime

The 2004-06-19 fix for who and pinky was incomplete, as ctime
has undefined behavior if the year precedes -999 or follows 9999.
Since we have to stop using ctime anyway, we might as well use
strftime and fix the FIXME, and support internationalized dates.

Include "hard-locale.h".
(time_format, time_format_width): New vars.
(time_string, print_line): Use them.
(main): Set them.
(time_string): Use localtime + strftime instead of
ctime, to avoid problems with years before -999 or after 9999.