RFC: DateTime::SpanSet new()

[fglock]

RFC: how to name these parameters to the 
DateTime::SpanSet->new() method:

#1 - Building a SpanSet from 
     2 recurrence callbacks:

  $set = new DateTime::SpanSet (
    starting_recurrence_sub => sub { ...... },
    ending_recurrence_sub =>   sub { ...... },
  );

#2 - Building a SpanSet from 
     2 DateTime::Set recurrences:

  $set = new DateTime::SpanSet (
    starting_recurrence_set => $dt_set_start,
    ending_recurrence_set =>   $dt_set_end,
  );

- Flavio S. Glock