Function deoptimize_value

test/expected/catch.hpp:6458–6460

        template <typename T>
        inline void deoptimize_value(T&& x) {
            keep_memory(&x);
        }

        template <typename Fn, typename... Args>
        inline auto invoke_deoptimized(Fn&& fn, Args&&... args) -> typename std::enable_if<!std::is_same<void, decltype(fn(args...))>::value>::type {