Add support for Finnish holidays Candlemas and Feast of the Annunciation

[ckunki]

• Kynttilänpäivä
• ilmestyspäivä

Example

(holiday-sexp
  '(let ((day (calendar-nth-named-day 1 0 2 year 2)))
     (if (equal day (caar (holiday-easter-etc -49)))
       (caar (holiday-easter-etc -56))
       day))
  "Kynttilänpäivä")

computes

• a pivot date: holiday float 1 SUN after 2 2 Kynttilänpäivä
• but only use pivot date, if not equal to holiday easter -49
• otherwise use holiday easter -56

potential syntax
holiday either float 1 Sun after FEB 2 of if equal to easter -49 then easter -56 Kynttilänpäivä

(holiday-sexp
  '(let ((day (calendar-nth-named-day 1 0 3 year 22)))
     (if (or (equal day (caar (holiday-easter-etc 0)))
         (equal day (caar (holiday-easter-etc -7))))
         (caar (holiday-easter-etc -14))
       day))
  "Marian ilmestyspäivä")

computes

• a pivot date: holiday float 1 Sun after MAR 22 Marian ilmestyspäivä
• but only use pivot date, if not equal to holiday easter 0 or holiday easter -7
• otherwise use holiday easter -14

potential syntax
holiday either float 1 Sun after MAR 22 of if equal to easter 0,easter -7 then easter -14 Kynttilänpäivä