ticket:10254: Added dtitvfmtsample.cpp, dtptngsample.cpp, and plurfmtsample.cpp. Update all/all.sln, dtitvfmt.h,dtptngen.h and plurfmt.h to embed the sample into the ICU4C API docs.

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@33953 251d0590-4201-4cf1-90de-194747b24ca1