Fix a bunch of int to unsigned int conversion warnings

Explicitely include all needed botan headers

Most importantely, include parsing.h, since read_cfg is not implicitely
included anymore in botan 2.3, and that does not compile.

Also do not included botan.h anymore, since it’s deprecated in botan 2.3

fix #3296

Drop support for botan < 2.0

fix #3274

Apply all the clang-tidy performance-* fixes

Refactoring louloulibs and cmake

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

Update the verify_certificate_chain code to work with botan >= 1.11.34 as well

Refactor load_certs()

Replace all include guards by #pragma once

It’s $CURRENT_YEAR

Style fix

Move all constructors at the top of classes

Rename BasicCredentialManager

Support a trusted SHA1 fingerprint to be configured for each IRC server

Provide an adhoc option to let user pass the cert verif for some IRC servers

Fix the build without botan, caused by credentials_manager

Verify the remote TLS certificates using the system-wide trusted CAs