- to use already a few c14 convenience details :
-> polymorphic std::plus, e.g.
boost::mpi::reduce (world, A,C, std::c14::plus<>(),0);
this plus determine the type by itself ...
-> errors on the type can be very cryptic on the gf.
-> add std::c14::make_unique
(equivalent of make_shared for unique_ptr).
