Allow block event calendar to display the next future event, instead of current month.

If an event is far in the future, the event calendar will be empty.
For sites relying on the calendar to notify of an upcoming event, skipping forward to that event when fetching a calendar would be more useful.
In 5.x I did something like:
case 0:
$time = _event_user_date();
if (arg(0) == 'event' && is_numeric(arg(1))) {
// follow event calendar
$year = (arg(1) ? arg(1) : gmdate('Y', $time));
$month = (arg(2) ? arg(2) : gmdate('m', $time));
$day = (arg(3) ? arg(3) : gmdate('d', $time));
$stamp = gmmktime(0, 0, 0, $month, $day, $year);
}
else {
// default to time of most recent future event
$result = db_query(db_rewrite_sql('SELECT event_start FROM {event} where event_start > %d'), time());
if ($first = db_fetch_object($result)) {
$stamp = $first->event_start;
}
else {
$stamp = _event_user_date();
}
}

6.x uses the date array at this point, so I suppose the timestamp would need conversion - in any case, I didn't offer a config option for this, so I hesitate to provide a diff ;)