libnetlink: comment out unused code; don't use 8k stack buffers

function                                             old     new   delta
ipaddr_modify                                       1305    1297      -8
do_iprule                                            963     955      -8
do_iproute                                          2193    2169     -24
xrtnl_dump_filter                                    418     391     -27
rtnl_talk                                            671     536    -135
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/5 up/down: 0/-202)           Total: -202 bytes

2 files changed