ticket:10051: Windows Critical Sections cleanup.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/andy@33781 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10051: Mutexes, fix bad platform ifdef

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/andy@33782 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10051 Restore stubs for deprecated user mutex functions.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/andy@33786 251d0590-4201-4cf1-90de-194747b24ca1