message: Add data pointer accessors for vector and matrix classes
  This changelist adds data pointer accessors for the vector and matrix classes, providing a more convenient API for converting data between representations (e.g. MaterialX and Eigen).
diff: @@ -207,6 +207,16 @@ template <class V, class S, size_t N> class VectorN : public VectorBase
  Iterator end() { return _arr.end(); }
  ConstIterator end() const { return _arr.end(); }
  + /// @}
  + /// @name Data Pointers
  + /// @{
  +
  + /// Return a pointer to the underlying data array.
  + S* data() { return _arr.data(); }
  +
  + /// Return a const pointer to the underlying data array.
  + const S* data() const { return _arr.data(); }
  +
  /// @}
  /// @name Static Methods
  /// @{
  @@ -492,6 +502,16 @@ template <class M, class S, size_t N> class MatrixN : public MatrixBase
  Iterator end() { return _arr.end(); }
  ConstIterator end() const { return _arr.end(); }
  + /// @}
  + /// @name Data Pointers
  + /// @{
  +
  + /// Return a pointer to the underlying data array.
  + S* data() { return _arr.front().data(); }
  +
  + /// Return a const pointer to the underlying data array.
  + const S* data() const { return _arr.front().data(); }
  +
  /// @}
  /// @name Static Methods
  /// @{
  