ticket:11139:Enable caching of DateTimePatternGenerator. Fix bug in DateTimePatternGenerator copy constructor.

git-svn-id: http://source.icu-project.org/repos/icu/icu@36582 251d0590-4201-4cf1-90de-194747b24ca1
ticket:11139: Add more performance tests.

git-svn-id: http://source.icu-project.org/repos/icu/icu@36583 251d0590-4201-4cf1-90de-194747b24ca1