It’s now easier to use. The distinction between a nick and a channel name is
based on the first character (by default it's '#' and '&'). The user doesn’t
have to worry about which separator to use anymore.

fix #3066

fix #3183

Not just part of it

Can’t remember why I did this, but that must be a stupid reason. Everything
must work even with a timeout of 0.

Because c-ares may close one of its socket, even if it’s not the one that
has the event. Otherwise we may not know when a socket has been removed from
our poller (automatically, when close()ed) and this leads to bugs.

This reverts commit 5328d080.