Implement a way to add callbacks, waiting for an IRC event to return an iq

Remove a duplicate “connection closed” message

Rewrite the whole IID usage

IRC users and channels are now distinguished by the separator used in the
IID (% or !).

ref #2468

Implement TLS support using Botan

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

Send (every 240s) a PING command to all connected irc servers

fix #2452

Send an error presence when the connection to the IRC server fails

Fix a by-one error in the CHANTYPES parsing

Use the CHANTYPES values to differentiate channel or user notices

It also happens to fix #2517 because this used to create buggy channels
named "auth" and stuf like that.

Add support for CHANTYPES isupport element, to know the prefixes of channels

SocketHandlers own the poller and add themself into it only when the socket is created

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.

Forward iq version results to IRC

Forward CTCP version request to XMPP

Use C++14 string_literals

Upgrade to C++14

NOTICE from channels are displayed in the channel, with a green "[notice]"

Add an explanatory topic on the dummy channel

Do not disconnect from the IRC server if the dummy channel is joined

Better way to leave the dummy room

Ability to leave the dummy channel

Correctly use the dummy channel whenever we interract with an empty-string chan