bug#45762: [PATCH] ocaml: Add ocaml-down and ocaml-ocp-index

[Julien Lepiller <julien@lepiller.eu>]

Pushed as b6529e189688ac8bc17c11cf24304fc554f5cb9b to
e3b71ee6dcb87452192fb4f5df9eeea31f1c1cfd. Thank you!

I changed the first two packages to use the git checkout instead of the
generated archive by github, because this archive is unstable:
sometimes it gets regenerated and has a different hash. git commits
don't do that.

I also updated ocp-indent to the latest version, and managed to get the
tests to run with the #:test-target argument. I also fixed the home
page (http -> https).

For the rest, I fixed the description by replacing markdown with
texinfo decoration `...` -> @code, @file, @command, ...

Thanks again for your contribution! If you run "guix pull" you should
be able to install ocaml-down :)

Lastly, if you use the git:send-email package, you should be able to
use the git send-email command, which should make sure to properly send
the patch description outside of the subject. Also, make sure to run
"guix lint" on the packages you submit next time, as it sometimes have
good suggestions to help improve the quality of your packages :)