ticket:10113: Added dtitvfmtsample.cpp. Updated the API document for DateIntervalFormat::createInstance (const UnicodeString &skeleton, const Locale &locale, UErrorCode &status) and 
DataIntervalFormat::createInstance (const UnicodeString &skeleton, const Locale &locale, const DateIntervalInfo &dtitvinf, UErrorCode &status)

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/bing@33780 251d0590-4201-4cf1-90de-194747b24ca1