This avoids bringing the dependency on ev on telescope-identity(1) and the tests as well.

libevent is a very cool library, I like the APIs and enjoy using it. However, telescope is not as large and doesn't have as many file descriptor, so libevent is quite ``too big'' for our needs. ev started as a small event loop on top of poll(2) for amused, and can be used here too, it just needed to grow the ability to handle several timers, as we need quite some on telescope (in fact, we use more timers than fds!)

it's redundant due to ibuf_borrow_str()

rework mark_nonblock so it sets the cloexec flag too and use it in control.c to avoid these flags. (which are expected to become available on a future revision of POSIX and are already widely available.) It's not an issue for telescope to do the socket/accept + fcntl dance because there aren't threads that can fork(2) (there are no threads at all!) reported by @sikmir at github https://github.com/omar-polo/telescope/commit/59ef79dd19611c7846b00427e6f2267c748ae290#r74498414