asio standalone support

[kassane]

Requested: #161
cc: @uNetworkingAB

[uNetworkingAB]

This is too specific and too much of a hack for something that eventually will become part of std. I would much rather support the standard C++ networking and dump the asio support entirely, than add ifdefs to support old and strange version of asio.

[kassane]

I know WG21 doesn't consider sticking to the asio on std.

The only purpose of the standalone version is not to use boost libraries even header-only.

ASIO is no longer on the standards track.

WG21 is currently considering a proposed standard networking based on P2300 senders and receivers. It is early stage, and there will be zero compatibility with ASIO. - @ned14

Reference

https://www.reddit.com/r/cpp/comments/13op38r/how_to_write_networking_code_now_that_will_be/jl739wr/?utm_source=share&utm_medium=mweb3x&utm_name=mweb3xcss&utm_term=1&utm_content=share_button

[uNetworkingAB]

Interesting, I see that they aren't getting along very well. But this really just strengthens my opinion on this - there are too many variants of ASIO and the only "famous" one is the Boost one.