PODSmallVector - fix uninitialized variable warnings. NFCI.

  static_assert(std::is_pod<T>::value,

                "T is required to be a plain old data type");

  T* First;

  T* Last;

  T* Cap;

  T Inline[N];

  T* First = nullptr;

  T* Last = nullptr;

  T* Cap = nullptr;

  T Inline[N] = {};

  bool isInline() const { return First == Inline; }