networking/libiproute/*: code shrink by optimizing numeric conversions

networking/libiproute/*: code shrink by optimizing numeric conversions
 and other misc stuff

function                                             old     new   delta
print_tunnel                                         660     656      -4
format_host                                            5       -      -5
get_unsigned                                          70      54     -16
get_u32                                               70      54     -16
do_iplink                                           1173    1151     -22
get_prefix                                           417     393     -24
print_rule                                           800     771     -29
print_addrinfo                                      1374    1342     -32
print_route                                         1745    1709     -36
iprule_modify                                        905     866     -39
iproute_modify                                      1105    1048     -57
get_integer                                           70       -     -70
parse_args                                          1684    1440    -244
------------------------------------------------------------------------------
(add/remove: 0/2 grow/shrink: 0/11 up/down: 0/-594)          Total: -594 bytes
   text    data     bss     dec     hex filename
 817378     476    7892  825746   c9992 busybox_old
 816784     476    7892  825152   c9740 busybox_unstripped