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

include/boost/beast/http/impl/chunk_encode.ipp

@@ -24,7 +24,7 @@ chunk_header::
 chunk_header(std::size_t size)
     : view_(
         size,
-        boost::asio::const_buffers_1{nullptr, 0},
+        boost::asio::const_buffer{nullptr, 0},
         chunk_crlf{})
 {
     BOOST_ASSERT(size > 0);
@@ -37,7 +37,7 @@ chunk_header(
     string_view extensions)
     : view_(
         size,
-        boost::asio::const_buffers_1{
+        boost::asio::const_buffer{
             extensions.data(), extensions.size()},
         chunk_crlf{})
 {
@@ -90,7 +90,7 @@ chunk_body<ConstBufferSequence>::
 chunk_body(ConstBufferSequence const& buffers)
     : view_(
         boost::asio::buffer_size(buffers),
-        boost::asio::const_buffers_1{nullptr, 0},
+        boost::asio::const_buffer{nullptr, 0},
         chunk_crlf{},
         buffers,
         chunk_crlf{})
@@ -104,7 +104,7 @@ chunk_body(
     string_view extensions)
     : view_(
         boost::asio::buffer_size(buffers),
-        boost::asio::const_buffers_1{
+        boost::asio::const_buffer{
             extensions.data(), extensions.size()},
         chunk_crlf{},
         buffers,