Drop basic_row

[tkem]

It's kind of awkward to use, and with C++17 serves no real purpose any more.
Also think about renaming mem_fn_row to simply row on C++11, should be reasonably forward-compatible with the C++17 implementation (except for overloaded member functions).

[tkem]

Renaming (and therefore effectively dropping mem_fn_row) turns out to be a burden in practice, since this will effectively break application code when moving to C++17. So both should be kept, and basic_row probably too for now.