Async initialization for DateFormat

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

Index: pkg/intl/data/dates/symbols/eu.json
===================================================================
--- pkg/intl/data/dates/symbols/eu.json	(revision 0)
+++ pkg/intl/data/dates/symbols/eu.json	(revision 0)
@@ -0,0 +1 @@
+{"DATEFORMATS":["EEEE, y'eko' MMMM'ren' dd'a'","y'eko' MMM'ren' dd'a'","y MMM d","yyyy-MM-dd"],"NARROWWEEKDAYS":["I","M","A","A","A","O","I"],"STANDALONESHORTMONTHS":["urt","ots","mar","api","mai","eka","uzt","abu","ira","urr","aza","abe"],"ERANAMES":["K.a.","K.o."],"FIRSTWEEKCUTOFFDAY":3,"NARROWMONTHS":["U","O","M","A","M","E","U","A","I","U","A","A"],"STANDALONESHORTWEEKDAYS":["ig","al","as","az","og","or","lr"],"FIRSTDAYOFWEEK":0,"STANDALONEWEEKDAYS":["igandea","astelehena","asteartea","asteazkena","osteguna","ostirala","larunbata"],"WEEKDAYS":["igandea","astelehena","asteartea","asteazkena","osteguna","ostirala","larunbata"],"QUARTERS":["1. hiruhilekoa","2. hiruhilekoa","3. hiruhilekoa","4. hiruhilekoa"],"ERAS":["K.a.","K.o."],"MONTHS":["urtarrila","otsaila","martxoa","apirila","maiatza","ekaina","uztaila","abuztua","iraila","urria","azaroa","abendua"],"TIMEFORMATS":["HH:mm:ss zzzz","HH:mm:ss z","HH:mm:ss","HH:mm"],"SHORTWEEKDAYS":["ig","al","as","az","og","or","lr"],"SHORTQUARTERS":["1Hh","2Hh","3Hh","4Hh"],"WEEKENDRANGE":[5,6],"STANDALONENARROWWEEKDAYS":["I","M","A","L","A","O","I"],"AVAILABLEFORMATS":null,"NAME":"eu","AMPMS":["AM","PM"],"STANDALONEMONTHS":["urtarrila","otsaila","martxoa","apirila","maiatza","ekaina","uztaila","abuztua","iraila","urria","azaroa","abendua"],"SHORTMONTHS":["urt","ots","mar","api","mai","eka","uzt","abu","ira","urr","aza","abe"],"STANDALONENARROWMONTHS":["U","O","M","A","M","E","U","A","I","U","A","A"]}