Enhance and stabilize binary_data interface

[sque]

Enhance and stabilize binary_data interface

[sque]

Proposed Stable Interface 1

binary_data

  binary_data(const binary_data &);
  binary_data & operator=(const binary_data &);

  binary_data operator+(const_mem_block &);
  binary_data operator+=(const_mem_block &);

  size_t find(const_mem_block &);
  binary_data sub_data(size_t start_offset, size_t desired_size);
  binary_data until(size_t desired_size);
  binary_data from(size_t offset);

  pointer c_array();
  const pointer c_array() const;
  size_t size();

  // Constants
  size_t npos;
  binary_data nothing;