Boost 1.55 (ubuntu 14) fails to compile because an iterator produce by
boost::adaptors::transformed() when std::ref to lambda is passed to
it do not match iterator concept. It cannot be default constructed
because std::reference_wrapper is not default constructable.
boost::range::min_element() never actually default construct it, but
concept is checked anyway. The patch fixes it by providing an explicit
functor that is default constructable.
Message-Id: <20170618131836.GD3944@scylladb.com>
72a4554dd9