introduce and use bb_basename()

introduce and use bb_basename()

function                                             old     new   delta
bb_basename                                            -      26     +26
sv_main                                             1226    1225      -1
passwd_main                                         1985    1983      -2
showdirs                                             482     478      -4
sendCgi                                             1811    1807      -4
make_device                                         1354    1350      -4
handleIncoming                                      2443    2439      -4
func_name                                             82      78      -4
service_name                                        2292    2285      -7
main                                                 909     901      -8
cmp_main                                             555     547      -8
test_main                                            434     422     -12
act                                                  228     216     -12
find_pair                                            180     164     -16
rmmod_main                                           298     280     -18
find_pid_by_name                                     156     134     -22
modprobe_main                                       1606    1576     -30
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/16 up/down: 26/-156)         Total: -130 bytes
   text    data     bss     dec     hex filename
 734933    3028   14400  752361   b7ae9 busybox_old
 734801    3028   14400  752229   b7a65 busybox_unstripped