websocket read returns the number of bytes inserted (API Change):

* read and async_read now return the number of bytes inserted
into the caller's buffer.

Actions Required:

* Change the signature of completion handlers used with
  websocket::stream::async_read to void(error_code, std::size_t)

test/websocket/doc_snippets.cpp

@@ -209,7 +209,7 @@ boost::asio::ip::tcp::socket sock{ios};
 //[ws_snippet_20
     multi_buffer buffer;
     ws.async_read(buffer,
-        [](error_code)
+        [](error_code, std::size_t)
         {
             // Do something with the buffer
         });