proftpd: Convert proftpd group to system scope

Proftpd is meant to be a system user, not a normal user of the
system so lets pass the correct parameters to the system.
Just add --system param when creating ftp group.

Signed-off-by: Qiang Chen <qiang.chen@windriver.com>
Signed-off-by: Jeff Polk <jeff.polk@windriver.com>
Signed-off-by: Joe MacDonald <joe@deserted.net>
lowpan-tools: fix do_install failure

We don't have a proper help2man so building the manpages fails; just
disable building them to fix this as we do elsewhere.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Joe MacDonald <joe@deserted.net>