Merge: nitpackage: create and check Makefile

This PR adds two new features to `nitpackage`:
* `--check-makefile`: check Makefiles existence for packages and executable modules
* `--gen-makefile`: create Makefiles for packages and executable modules

As example I added new Makefiles (4f948e3) to all lib/ project if none was found.
I also updated some Makefiles from my projects (dbacfc0).

Please only consider the 4 last commits as the rest belongs to #2652, #2653, #2656 and #2657.

Pull-Request: #2662
Reviewed-by: Jean Privat <jean@pryen.org>