Linking for Lwt_unix

[antoinepouille]

I had a hard time finding out how to use Lwt_unix. I needed to link with lwt.unix.

I couldn't find this anywhere, including https://ocsigen.org/lwt/5.5.0/api/Lwt_unix https://github.com/ocsigen/lwt/blob/96cdc8346116dd1144d99225335c504d173a0236/src/unix/lwt_unix.cppo.mli and https://github.com/ocsigen/lwt

Maybe this would help to include it?

Cheers

EDIT: lwt.unix is mentioned there https://ocsigen.org/lwt/5.5.0/manual/manual , I didn't see it at a glance
I still think this could be made more explicit

[raphael-proust]

The documentation would surely benefit from some imporvement.

There was also a half-baked plan to make the packaging better by having a better match between the packages and the libraries.