ticket:10999: avoid giving \uhhhh to the C++ compiler

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk@36517 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10999: mark formatMeasuresPer() as Technology preview

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk@36518 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10992: BRS line 20, Check/fix non-stable API macros (U_HIDE_DRAFT_API and others)

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk@36520 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10992: Updated APIChangeReportml.

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk@36521 251d0590-4201-4cf1-90de-194747b24ca1