Building using c++ 17 produces warnings about deprecated std::iterator

[PlatypusTechUK]

When building with C++ 17 warnings are produced complaining std::iterator is deprecated (See https://en.cppreference.com/w/cpp/iterator/iterator, https://stackoverflow.com/questions/43268146/why-is-stditerator-deprecated and https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0174r1.html#2.1)

Given writing the typedefs out longhand isn't particularly long, doing so would be helpful for users on newer standards than C++ 11