traceroute: set IP_PKTINFO to see correct local IP of received pkt (fixes -v display)

Also, assorted code shrink:

function                                             old     new   delta
traceroute_init                                     1210    1172     -38
common_traceroute_main                              2141    2091     -50
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-88)             Total: -88 bytes

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