Fixing some issues with DateField.selectableRange. Between Flex 2 and Flex 3, we restricted some code in commitProperties to only update the days when the date was valid. Unfortunately, we were allowing the user to increment and decrement the month to invalid dates. So we would increment, but the dates wouldn't redraw correctly, and we'd be left in a funky state. To fix this, we just restricted the up/down arrows for years and months to be more restrictive (as restrictive as the commitProperties() check).