* Increases consistency with other iterators (e.g. df_iterator, po_iterator...)
* It's shorter
* We don't name classes by the implementation, we name it for the interface!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8273 91177308-0d34-0410-b5e6-96231b3b80d8