ticket:10301 Remove singleton classes, convert existing usage to UInitOnce

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk@34032 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10301 Remove nearly empty mutex.cpp file.

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk@34034 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10252: Use the new converter to generate synthetic locales and .mk files.

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk@34035 251d0590-4201-4cf1-90de-194747b24ca1