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

fix #2452

TimedEventsManager is now a singleton

Timed events can have a name, and can be canceled based on their name

Use libuuid to generate unique IDs for iq and adhoc sessions

Use pkg-config first to find libraries

Add missing files (for adhoc command support)

XmlNode::get_children, to get a list of matching children instead of the first

XmlNode’s copy constructor now recursively copies the children nodes as well

Implement the support for adhoc commands

We have two basic example commands. But it’s not entirely finished because
there are some error checks that we don’t do.

ref #2521

Change the way the namespaces are handled in the XmlNode class

Move the logging + config test on first position

Use a timed event to force the exit 2 seconds after an exit signal is received

fix #2469

Introduce the timed events

On connection in-progress, save the whole addrinfo struct, not just ai_addr

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

Only close/unmanage the socket if we are connected/connecting

Since the socket is now only created and managed whenever the connection is
being established, we only close the socket and if it was created (we use -1
to denote the fact that is not yet created, or has been closed) and we only
unmanage the socket if it is effectively managed.

fix #2529

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

Support IPv6 connections

fix #2522