Add boost::move_only_function for C++11

[denzor200]

Analogue of std's one ( https://en.cppreference.com/w/cpp/utility/functional/move_only_function )

[pdimov]

There have been a few requests for this already. It's a bit borderline because Compat is supposed to not contain interface types as they would cause ABI issues if selectively mapped to std counterparts with using, but user demand for move_only_function probably justifies bending the rules for it.