ticket:10070: Add plain C wrappers for Region class

git-svn-id: http://source.icu-project.org/repos/icu/icu@33520 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10070: Fix crash due to bug in uenum_next that only affects some compilers

git-svn-id: http://source.icu-project.org/repos/icu/icu@33521 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10070: And handle NULl return from uregion_getContainedRegions... while I am at it

git-svn-id: http://source.icu-project.org/repos/icu/icu@33522 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10051 InitOnce and UMTX_CHECK, work in progress

git-svn-id: http://source.icu-project.org/repos/icu/icu@33523 251d0590-4201-4cf1-90de-194747b24ca1