Method CustomSmartPtr

test/embind/embind_test.cpp:1686–1688

template<typename T> class CustomSmartPtr {
public:
  CustomSmartPtr() : CustomSmartPtr(nullptr) {
    std::fill(d_, d_ + N_, Valid);
  }

  explicit CustomSmartPtr(T* t) : ptr_(t) {
    std::fill(d_, d_ + N_, Valid);