* calendar/icalendar.el (icalendar-export-sexp-enumerate-all)
(icalendar-export-sexp-enumeration-days): New
(icalendar-export-region): `icalendar--convert-to-ical' now
returns a cons cell or a list of cons cells.
(icalendar--convert-to-ical): Take care of
`icalendar-export-sexp-enumerate-all'. Return (a list of) cons
cells.
(icalendar--convert-ordinary-to-ical),
(icalendar--convert-weekly-to-ical),
(icalendar--convert-yearly-to-ical),
(icalendar--convert-block-to-ical),
(icalendar--convert-block-to-ical),
(icalendar--convert-float-to-ical),
(icalendar--convert-cyclic-to-ical),
(icalendar--convert-anniversary-to-ical): Return cons cell.
(icalendar--convert-sexp-to-ical): Enumerate evaluated sexp
entries. Return (list of) cons cells.