Implemented NSCalendar (Autoindigestion) methods.

Renamed -fiveNewYearsAgoForDate: method on NSCalendar (Autoindigestion)
category to -fiveNewYearsDaysAgoForDate.

Created real implementations for -fiveNewYearsDaysAgoForDate: and
-nextYearForDate: methods.  Added -previousNewYearsDayForDate: method
to the category.

Added unit tests for both old and new methods on the category.