Method construct

example/http/server/fast/fields_alloc.hpp:169–174

#if defined(BOOST_LIBSTDCXX_VERSION) && BOOST_LIBSTDCXX_VERSION < 60000
    template<class U, class... Args>
    void
    construct(U* ptr, Args&&... args)
    {
        ::new(static_cast<void*>(ptr)) U(
            std::forward<Args>(args)...);
    }

    template<class U>
    void