ticket:10295 Mutex ucln_registerCleanup to clear thread sanitizer errors.

git-svn-id: http://source.icu-project.org/repos/icu/icu@35655 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10844 Add Regex test case.

git-svn-id: http://source.icu-project.org/repos/icu/icu@35657 251d0590-4201-4cf1-90de-194747b24ca1