Optimise conversion of rvalue cypclass smart pointers to raw cypclass pointers

Cython/Utility/CyObjects.cpp

@@ -164,13 +164,19 @@
                 return uobj;
             }
 
-            operator T*() const {
+            operator T*() const& {
                 if (uobj != nullptr) {
                     uobj->CyObject_INCREF();
                 }
                 return uobj;
             }
 
+            operator T*() && {
+                T* obj = uobj;
+                uobj = nullptr;
+                return obj;
+            }
+
             template <typename U>
             bool operator==(const Cy_Ref_impl<U>& rhs) const noexcept {
                 return uobj == rhs.uobj;