GtkCalendar: Pushed to its limits, it fails miserably

GtkCalendar uses GDateTime, from 0001-01-01 to 9999-12-31.

If a user crosses the limits, GtkCalendar goes unusable.

Select 9999-12-24. The easiest way is to call gtk_calendar_select_day(). Try going to the next month or the next year.

Select 0001-01-15. The easiest way is to drop the date. Try going to the previous month or previous year.

The calendar is no longer usable.

The calendar must remain alive and eventually warn about limits crossing.