nc: minor code shrink

nc: minor code shrink

function                                             old     new   delta
dolisten                                             731     737      +6
tmtravel                                              32      21     -11
catch                                                 75      64     -11
oprint                                               272     229     -43
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/3 up/down: 6/-65)             Total: -59 bytes
   text    data     bss     dec     hex filename
 676698    3340   13936  693974   a96d6 busybox_old
 676650    3340   13936  693926   a96a6 busybox_unstripped