que veut dire le paragraphe suivant? et en particulier set-group-id bit.
- Add a new group called `mailman'. Typically this is added to
your /etc/group file. The Mailman files will be installed under
the `mailman' group, with the set-group-id bit. This is so both
the web based and mail based programs will have the proper write
permissions. If groupname `mailman' is already in use, choose
something else unique and see the --with-ownergroup below.
