Request for forward declarations header

[Andrey Semashev]

I'm trying to implement a library that does something over the network. It exposes an interface that allows to supply local and remote host addresses to work with. However, as ASIO is header-only and depends on system headers, such as windows.h, I don't want to force the users of my library to include the whole implementation of ASIO and the system headers by using my library interface.

A header with forward declarations of the most commonly used ASIO types could help me to achieve this goal. In particular, forward declarations of IP address classes would be helpful.