ticket:10532 ICU Charset Detector, port UTF-16 enhancements from Java to C

git-svn-id: http://source.icu-project.org/repos/icu/icu@34730 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10553: RelativeDateFormat copy constructor was incomplete

git-svn-id: http://source.icu-project.org/repos/icu/icu@34731 251d0590-4201-4cf1-90de-194747b24ca1