ticket:10439: add comment about why volatile is here


git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@34476 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10442: Fix to have proper #ifndef U_HIDE_DRAFT_API around the now-draft-again API

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@34480 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10442: Revert previous change, the whole class is inside #ifndef U_HIDE_DRAFT_API

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@34481 251d0590-4201-4cf1-90de-194747b24ca1