* is_completion_handler is deprecated
* type_traits.hpp is a deprecated include
These items will be removed in the next version
* Include the new header file for the types needed:
- stream_traits.hpp
- file_base.hpp
* Use std::is_invocable instead of is_completion_handler
fix#1416
* Calls to buffer_copy are qualified as net::buffer_copy
* Calls to buffer_size are made unqualified, permitting
argument dependent lookup to take effect.
