[boost] [config] std::unique_ptr, std::ref detection?

Suppose I want to implement a shared_ptr constructor taking std::unique_ptr. To avoid breaking pre-C++11 compilers, I need to, at least, know whether <memory> contains std::unique_ptr. (I'd also like to know if there's std::ref in <functional> because the specification of the constructor uses it.) But the config library doesn't seem to provide a way. There's no macro for std::unique_ptr, and there's no macro for "generic C++11 compiler and library".