ticket:9101: test CE & sort key validity in collationtest.cpp using CollationRootElements & getTailoredSet() rather than the rule parser; fix CollationDataReader & getTailoredSet()

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/markus@34657 251d0590-4201-4cf1-90de-194747b24ca1