warning: typedef 'iterator' locally defined but not used

[mikepurvis]

We get tons of these in our builds:

containers.hpp:256:45: warning: typedef 'iterator' locally defined but not used [-Wunused-local-typedefs]
   typedef typename Implementation::iterator iterator;
containers.hpp:292:45: warning: typedef 'iterator' locally defined but not used [-Wunused-local-typedefs]
   typedef typename Implementation::iterator iterator;
containers.hpp:329:45: warning: typedef 'iterator' locally defined but not used [-Wunused-local-typedefs]
   typedef typename Implementation::iterator iterator;

[stonier]

Handling the 'unused' compile time asserts for templates is a bit trickier...leaving this open for that.