ticket:10357: only show 'are you missing data' once


git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@34197 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10345: make formatting of a Formattable currency thread safe.. by cloning.  makes unum_formatDoubleCurrency also slow. 

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@34200 251d0590-4201-4cf1-90de-194747b24ca1