Allow supplementary groups to be set via the /etc/default/useradd config
file. Allowing an administrator to set additonal groups via the GROUPS
configurable and control the default behaviour of useradd.
The content of the man pages however is dependent on compile flags. So the
pre-built ones might not fit your version of shadow. To build them yourself use
--enable-man. Furthermore the following build requirements will be needed:
e8d2bc8d8b