busybox

iproute: update help text, add commented-out code for unsupported options

function                                             old     new   delta
packed_usage                                       31327   31372     +45
do_iproute                                           132     157     +25
iproute_modify                                      1162    1164      +2
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 72/0)               Total: 72 bytes

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