2ba61723

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

ical-recurrence: add a scenario calendar for a date-valued RecurrenceDateTimes

The unit test on this branch covers the bug through recurEvents directly.
This covers it through the golden scenario harness as well, which is how
the other recurrence fixtures in this package are expressed and which
also exercises rendering the resulting occurrences back out.

The golden takes the all-day reading: the value type of the RDATE says
DATE, so the added instance is all-day and spans one day.  Coercing the
instance to the event's time of day instead, preserving the exact one
hour duration, would be defensible too; then the golden becomes
DTSTART;VALUE=DATE-TIME:20200102T000000Z with a DTEND an hour later.