clang-modernize: Clean up help output

Now hiding options clang-modernize doesn't use and didn't create. Version
printer specialized for clang-modernize. EXAMPLES text fixed and brought
up-to-date.

Differential Revision: http://llvm-reviews.chandlerc.com/D1849



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@192253 91177308-0d34-0410-b5e6-96231b3b80d8