types: remove internal make_unique implementation

we can use the c++1y implementation instead which is a lot more robust.

types.hpp

@@ -32,13 +32,6 @@ constexpr size_t elems(const T (&)[N])
     { return N; }
 
 
-template <class T, class...Args>
-std::unique_ptr<T>
-make_unique(Args&&... args) {
-    return std::unique_ptr<T> (new T(std::forward<Args>(args)...));
-}
-
-
 //-----------------------------------------------------------------------------
 template <class T>
 T