Wrong Event Macro

[YukunJ]

In the Acceptor's event setter, used EPOLL_CTL_ADD instead of EPOLLIN as the read event signal. This is incorrect. It works before because they share the same value. But this is not portable.

Should distinguish the "operator" EPOLL_CTL_ADD and event signal EPOLLIN.

Same applies to MacOS Kqueue part.

Thanks to "大橘为重" on Zhihu platform for raising this issue to my attention.