- added DT::Set count()
- fixed DT::SpanSet duration()
- methods that accepted a DT object, now accept a list of DT objects.
Suggested by Ben Bennet, I think.
- added _callback_next - "previous-only recurrences"
- optimizes intersection of recurrence with span
- internal 'S::I' recurrence class
- small fix in DT::Set clone()
- DateTime::Set uses DateTime infinity constants; max and min now return
DateTime::Infinite::Future/Past objects.
- DateTime::Span uses DateTime infinity constants; max and min now return
DateTime::Infinite::Future/Past objects.
Docs update to explain 'max()' value when a span is built using 'before'.
- added method set_time_zone()
- clone() is documented
Approved by: demon (mentor)
