GtkCalendar::select_day
void select_day(int day);
select_day() specifies the
day number that will be selected (i.e. highlighted).
Note that if there are no further instructions, the same day will be
highlighted throughout the months and years in the calendar.
The default selected day is 1, with the range
being 1 to 31. Selecting an
impossible day within that range - e.g. February 30th - does not
return an error message, as the day number is not associated with the
month and year information in this method.
