ticket:10017: Merge r33567 to r33623 from trunk.

git-svn-id: http://source.icu-project.org/repos/icu/icu@33624 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10051 InitOnce, platform tweaks.

git-svn-id: http://source.icu-project.org/repos/icu/icu@33625 251d0590-4201-4cf1-90de-194747b24ca1