ticket:10182: build time mutexes, create development branch.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/andy@34036 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10182: User Mutex prototype, work in progress.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/andy@34037 251d0590-4201-4cf1-90de-194747b24ca1