* 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.
The nested function lowest_layer and nested type lowest_layer_type
are removed from all stream layers.
Actions Required:
* Remove lowest_layer and lowest_layer_type from user-defined streams.
* Use the get_lowest_layer free function and the lowest_layer_type trait
as needed.
