message: [c++] Sort OutputBuffer init list and members uniformly
  This make the init list order match the real order of initialization,
  avoiding a warning from Clang/GCC.
diff: @@ -80,6 +80,7 @@ public:
  /// @brief Construct OutputMemoryStream using specified allocator instance
  explicit OutputMemoryStream(const A& allocator = A())
  : _allocator(allocator),
  + _buffer(),
  _bufferSize(0),
  _rangeSize(0),
  _rangeOffset(0),
  @@ -98,12 +99,12 @@ public:
  uint32_t minChanningSize = 32,
  uint32_t maxChainLength = (uint32_t)-1)
  : _allocator(allocator),
  + _buffer(buffer),
  _bufferSize(size),
  _rangeSize(0),
  _rangeOffset(0),
  _minChainningSize(minChanningSize),
  _maxChainLength(maxChainLength),
  - _buffer(buffer),
  _rangePtr(_buffer.get()),
  _blobs(allocator)
  {
  