Class PrivateOpNew

tests/test_copy_move.cpp:252–263

#70 compilation issue if operator new is not public - simple body added but not needed on most compilers; MSVC and nvcc don't like a local struct not having a method defined when declared, since it can not be added later.

    // struct not having a method defined when declared, since it can not be
    // added later.
    struct PrivateOpNew {
        int value = 1;

    private:
        void *operator new(size_t bytes) {
            void *ptr = std::malloc(bytes);
            if (ptr) {
                return ptr;
            }
            throw std::bad_alloc{};
        }
    };
    py::class_<PrivateOpNew>(m, "PrivateOpNew").def_readonly("value", &PrivateOpNew::value);
    m.def("private_op_new_value", []() { return PrivateOpNew(); });
    m.def(