ticket:9914: Create branch in ICU4C.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@33219 251d0590-4201-4cf1-90de-194747b24ca1
ticket:9914: Add C++ code to handle variations of y in Date interval format skeletons.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@33226 251d0590-4201-4cf1-90de-194747b24ca1