Merge: Use self in the FFI

As requested by everyone, replace the id `recv` by `self` in all Nit FFIs, and their users.

This PR must be integrated before regenerating c_src and using the light FFI in bootstrap critical code.

There is a few commits to update the style of files that caused white space errors.

Pull-Request: #1399
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Jean-Philippe Caissy <jpcaissy@piji.ca>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>