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- Rename all Find*.cmake files to uppercase, to make things more consistent,
  and fix some issues with them (notably the REQUIRED flag)

- Rename SYSTEMDDAEMON to SYSTEMD and only use the libsystemd instead of
  libsystemd-daemon because it's deprecated for a long time now

- Provide a WITH_* and WITHOUT_* switch for all optional dependencies

- Document things in the INSTALL file

Use them to build without linking to them, even if they are on your system

fix #2551

See CMP0037

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

Also we cannot use both this feature and valgrind at the same time.
So, I’ll just specify this flag myself when I need it, this doesn’t
need to be there by default

Use ccmake, or cmake -i, or cmake -DPOLLER=EPOLL, for example