ping: stop using data/bss

ping: stop using data/bss

function                                             old     new   delta
ping_main                                            375     392     +17
unpack_tail                                          317     320      +3
ping4                                                525     528      +3
ping6                                                772     773      +1
sendping6                                             99      98      -1
sendping4                                            184     183      -1
myid                                                   2       -      -2
sendping_tail                                        154     151      -3
tsum                                                   4       -      -4
tmin                                                   4       -      -4
tmax                                                   4       -      -4
source_lsa                                             4       -      -4
pingsock                                               4       -      -4
pingcount                                              4       -      -4
ntransmitted                                           4       -      -4
nrepeats                                               4       -      -4
nreceived                                              4       -      -4
if_index                                               4       -      -4
hostname                                               8       4      -4
dotted                                                 4       -      -4
datalen                                                4       -      -4
pingaddr                                              28       -     -28
rcvd_tbl                                             128       -    -128
------------------------------------------------------------------------------
(add/remove: 0/15 grow/shrink: 4/4 up/down: 24/-215)         Total: -191 bytes
   text    data     bss     dec     hex filename
 679835    2728   16736  699299   aaba3 busybox_old
 679851    2720   16536  699107   aaae3 busybox_unstripped