Fix ranges test infrastructure

[miscco]

We get errors due to ambiguous symbols of test::iterator and std::iterator (thanks using namespace std;)
Explicitely pull in test::iterator and test::range for good measure too

[StephanTLavavej]

I have traditionally preferred to name test machinery differently than Standard machinery to avoid any potential for ambiguity (as I've been a huge fan of using namespace std; in tests); MeowIterator and to a slightly lesser extent meow_iterator are clearly non-Standard. That said, I certainly defer to @CaseyCarter on ranges test conventions.

[CaseyCarter]

Thanks for the cleanup, @miscco!