9b73b84b

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

ical-recurrence: keep the week day of a numeric ByDay

@
The BYDAY rule part
MUST NOT be specified with a numeric value with the FREQ rule part
set to YEARLY when the BYWEEKNO rule part is specified.
@

The number is meaningless once BYWEEKNO has fixed the week, so discard
the number and keep the week day rather than discarding the rule part.

Dropping it entirely was worse than ignoring the rule part: with no week
days left, the BYWEEKNO branch of yearlyDayCandidate falls back to all of
Monday to Sunday, which widens the recurrence set to every day of the
week instead of narrowing it.