Fix a bunch of int to unsigned int conversion warnings

Remove a useless getter

add 'verify_certificate' as possible configuration token for policy files
 This lets the user configure a per-domain certificate validation policy

Use our botan gh#1276 workaround only for botan < 2.4

fix #3320

Add a workaround for https://github.com/randombit/botan/issues/1276

ref #3278

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

Avoid any potential int overflow

Make botan’s policy configurable from a file

fix #3244

Better way to init the msghdr fields

Explicitely init the msghdr fields, to be compatible with any implementation

Apply all the clang-tidy misc-* fixes

Apply all the clang-tidy modernize-* fixes

Refactoring louloulibs and cmake

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

Pass the shared_ptr by reference, to avoid useless copies

Don’t use global static members but functions that return a reference to an internal static object

See https://github.com/randombit/botan/issues/761

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

Use the new botan 1.11.32 Tls::Client API (but stay compatible with older ones)

TLS: Enable ecc point compression

If available in Botan.

There is an issue where, if botan supports it but we don’t enable it, then
the TLS handshake may fail with some servers

Move all the connect() logic from TCPSocketHandler into a subclass

This way, TCPSocketHandler only deal with the message sending/receiving, not
the connect() or anything else.  This will be used for implementing servers
(because when a client is accepted, we don’t need all the connect() and dns
resolution stuff).