Async initialization for DateFormat

pkg/intl/data/dates/symbols/pl.json

Index: pkg/intl/data/dates/symbols/pl.json
===================================================================
--- pkg/intl/data/dates/symbols/pl.json	(revision 0)
+++ pkg/intl/data/dates/symbols/pl.json	(revision 0)
@@ -0,0 +1 @@
+{"DATEFORMATS":["EEEE, d MMMM y","d MMMM y","d MMM y","dd.MM.yyyy"],"NARROWWEEKDAYS":["N","P","W","Ś","C","P","S"],"STANDALONESHORTMONTHS":["sty","lut","mar","kwi","maj","cze","lip","sie","wrz","paź","lis","gru"],"ERANAMES":["p.n.e.","n.e."],"FIRSTWEEKCUTOFFDAY":3,"NARROWMONTHS":["s","l","m","k","m","c","l","s","w","p","l","g"],"STANDALONESHORTWEEKDAYS":["niedz.","pon.","wt.","śr.","czw.","pt.","sob."],"FIRSTDAYOFWEEK":0,"STANDALONEWEEKDAYS":["niedziela","poniedziałek","wtorek","środa","czwartek","piątek","sobota"],"WEEKDAYS":["niedziela","poniedziałek","wtorek","środa","czwartek","piątek","sobota"],"QUARTERS":["I kwartał","II kwartał","III kwartał","IV kwartał"],"ERAS":["p.n.e.","n.e."],"MONTHS":["stycznia","lutego","marca","kwietnia","maja","czerwca","lipca","sierpnia","września","października","listopada","grudnia"],"TIMEFORMATS":["HH:mm:ss zzzz","HH:mm:ss z","HH:mm:ss","HH:mm"],"SHORTWEEKDAYS":["niedz.","pon.","wt.","śr.","czw.","pt.","sob."],"SHORTQUARTERS":["K1","K2","K3","K4"],"WEEKENDRANGE":[5,6],"STANDALONENARROWWEEKDAYS":["N","P","W","Ś","C","P","S"],"AVAILABLEFORMATS":null,"NAME":"pl","AMPMS":["AM","PM"],"STANDALONEMONTHS":["styczeń","luty","marzec","kwiecień","maj","czerwiec","lipiec","sierpień","wrzesień","październik","listopad","grudzień"],"SHORTMONTHS":["sty","lut","mar","kwi","maj","cze","lip","sie","wrz","paź","lis","gru"],"STANDALONENARROWMONTHS":["s","l","m","k","m","c","l","s","w","p","l","g"]}