counting_iterator used as a forward iterator in <algorithm> generates warning in C++17

[luke-sterkowicz]

Following results in iterator_adaptor.hpp(318,1): warning C4244: '+=': conversion from '__int64' to 'Base', possible loss of data

std::for_each(std::execution::par, boost::counting_iterator<int>(0), boost::counting_iterator<int>(10), [&](int) {});