busybox

udhcp: tweak config order and menu item names

All other applets are listed simply by their name, no reason why
dumpleases doesn't do that.

Group all udhcpd feature options directly after it.

Put "NOT READY" into udhcpc6 item (some users actually tried to use it,
and complained).

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>