Hi Yves,

If you're talking about calling superuser rights for another user through Python:

 self.sudo(user.id)
self.sudo()   # This will use the SUPERUSER_ID by default
# or
self.env['res.partner'].sudo().create(vals)

There is some documentation about this, which you can find here: http://odoo-new-api-guide-line.readthedocs.org/en/latest/environment.html 
If you're talking about creating a new user, from the view, you should simply create a new user and grant it all rights under settings > users.

Yenthe

answer: I think that superuser user rights are granted when user_id = 1

in Settings-->Users

There is a drop down against Administration set that drop down to Settings

Following change will set user to superuser