When set to true, the realname and username are extracted (by default) from
the user’s JID

fix #3136

fix #3068

Each IrcClient callback has a max and min size of argument, we call the
callback only if the parsed message has a correct number of arguments,
otherwise it is ignored (with a warning logged).

ref #2472

This way, the users can receive the result of any IRC command (although not
parsed nor formatted in anyway) when biboumi doesn’t support it

fix #2884

Messages received on an IRC server JID are forwarded as raw IRC messages.

fix #2486

ref #2472

Because we need to wait for the welcome message, when we connect to the
server, before sending the JOIN command, we need to also save the value of
the password to reuse it when we actually send the JOIN command

fix #2882

fix #2576

SocketHandler has been renamed to TCPSocketHandler
SocketHandler is now a simple interface with a few methods, used only by
Poller.

This way we can inherite from the new SocketHandler class, to handle other
types of sockets, and still make them manageable by the poller without any
change in the Poller class.

For now, it tries two TLS ports and then connects to the non-tls port.  In
the future we would like the user to be able to configure that.

fix #2435

fix #2452

We want to call socket() with the parameters provided by getaddrinfo, so we
can’t addd the fd into the poller immediately. We need to wait the
connection attempt, and then the SocketHandler can call add_socket_handler
itself, if the connection succeeds, or is in progress.

CHANMODES and PREFIX only

We append each line to a string, and when the MOTD is
complete, we send that string at once.