Use std::forward_list instead of std::list, and implement size concept like boost::container::slist does.

Introduce some helper classes (ascs::socket2, socket3 and socket4) to reduce the number of template parameters.
Refactoring: move unpacker and strand from tcp::socket_base and udp::socket_base to ascs::socket.

Fix bug: if virtual bool on_msg_handle(OutMsgType&) returns false (means the message is not handled), the message will lost and never be re-dispatched.
Member variables refactoring.

Fix bug: queue::size_in_byte() may return wrong data with macro ASCS_SYNC_RECV or ASCS_SYNC_DISPATCH.

Fix infinite waiting after sync message sending or receiving failed.

Return the concept of 'size' and 'empty' in class queue to the Container's, and introduce new concept 'size_in_byte' to represent the memory size occupied by the queue.

Optimize class queue.

Promote queue's performance.

direct_send_msg support batch operation.
Introduce virtual function type_name() and type_id() to ascs::socket, they can identify whether a given two ascs::socket has the same type.
Drop the native parameter from i_packer::pack_msg(msg_type&& msg, ...).

Introduce virtual function pack_header to i_packer, it just pack headers.
Add an overload to send_(native_)msg, safe_send_(native_)msg, sync_send_(native_)msg and sync_safe_send_(native_)msg respectively, it accepts a in_msg_type&& parameter,
 this will reduce one memory replication (needs i_packer::pack_header).
Drop ascs::list which was implemented by ascs before, just simply use std::list, which means list::size() will not be called any more.