ticket:10320 API for getting/setting number format override in date formatting

git-svn-id: http://source.icu-project.org/repos/icu/icu@36097 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10802:Added unitonce and mutex to cache. condition variables still stubbed out.

git-svn-id: http://source.icu-project.org/repos/icu/icu@36099 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10948 Condition Variables, changes from PMC review of proposal.

git-svn-id: http://source.icu-project.org/repos/icu/icu@36100 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10948 Condition Variables, merged from development branch.

git-svn-id: http://source.icu-project.org/repos/icu/icu@36101 251d0590-4201-4cf1-90de-194747b24ca1