ticket:10805 Use InitOnce in Region class. Fixes threading problem in initialization.

git-svn-id: http://source.icu-project.org/repos/icu/icu@35653 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10295 remove unneeded development branch.

git-svn-id: http://source.icu-project.org/repos/icu/icu@35654 251d0590-4201-4cf1-90de-194747b24ca1