Avoid adding more that one “XMPP reconnection” timed event at the same time

Fix a semblance of infinite and busy loop, that could occur if biboumi’s
poller is woken up multiple times while the XMPP server is not reachable.

Apply all the clang-tidy modernize-* fixes

Refactoring louloulibs and cmake

Use OBJECT libraries
Remove the louloulibs directory
Write FOUND variables in the cache

Replace all include guards by #pragma once

It’s $CURRENT_YEAR

Remove all usage of std::list

Style fix

Move all constructors at the top of classes

louloulibs is directly included, instead of being a submodule

Because this is a nightmare to manage