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
fix#773
* buffer_cat is renamed to buffers_cat
* buffer_cat_view is renamed to buffers_cat_view
Actions Required:
* Use buffers_cat instead of buffer_cat
* Use buffers_cat_view instead of buffer_cat_view
fix#773
* buffer_prefix is renamed to buffers_prefix
* buffer_prefix_view is renamed to buffers_prefix_view
Actions Required:
* Use buffers_prefix instead of buffer_prefix
* Use buffers_prefix_view instead of buffer_prefix_view
* The drain_buffer dynamic buffer is no longer a public interface.
Actions Required:
* Replace code which uses drain_buffer. For websocket::stream,
it is no longer necessary to manually drain the connection
after closing.
