This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
``the last Monday in April'
- handle easter
new options
-f calendarfile
-A days
-B days
Calendar HOME directory ~/.calendar
don't sent mail if ~/.calendar/nomail exist