title: boost::asio::buffer how to iterate over the bytes
body: <p>I am trying to implement a function that takes a boost::const_buffer and iterates over its bytes in a loop.  I saw that there is a buffers iterator, but it seems to be applicable for boost::asio::buffers_type.  I didn't find any examples for simple traversal of a buffer.</p>
  
  <p>So, is it the standard way to access the buffer via buffer_cast into a native type such as char* and then traverse it by traditional methods?  Or is there any direct helper function to do this?</p>