Update for Net-TS Asio (API Change):

fix #769

The following classes are removed:

* handler_type
* async_result
* async_completion
* is_dynamic_buffer
* is_const_buffer_sequence
* is_mutable_buffer_sequence
* handler_alloc

Actions Required:

* Use BOOST_ASIO_HANDLER_TYPE instead of handler_type
* Use BOOST_ASIO_INITFN_RESULT_TYPE instead of async_result
* Use boost::asio::async_completion
* Use boost::asio::is_dynamic_buffer
* Use boost::asio::is_const_buffer_sequence
* Use boost::asio::is_mutable_buffer_sequence
* boost::asio::associated_allocator_t replaces handler_alloc

test/doc/exemplars.cpp

@@ -53,7 +53,7 @@ struct BodyReader
 {
 public:
     /// The type of buffer returned by `get`.
-    using const_buffers_type = boost::asio::const_buffers_1;
+    using const_buffers_type = boost::asio::const_buffer;
 
     /** Construct the reader.