HTTP reads and writes return bytes transferred (API Change):

* HTTP read and write operations now return the
  number of bytes transferred to or from the stream.

Actions Required:

* Modify HTTP read and/or write completion handlers to receive
  the extra std::size_t bytes_transferred parameter.

test/beast/http/read.cpp

@@ -329,7 +329,7 @@ public:
         handler() { ++count(); }
         ~handler() { --count(); }
         handler(handler const&) { ++count(); }
-        void operator()(error_code const&) const {}
+        void operator()(error_code const&, std::size_t) const {}
     };
 
     void