bc: code shrink

bc: code shrink

function                                             old     new   delta
bc_program_name                                       67      63      -4
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-4)               Total: -4 bytes
   text	   data	    bss	    dec	    hex	filename
 981372	    485	   7296	 989153	  f17e1	busybox_old
 981368	    485	   7296	 989149	  f17dd	busybox_unstripped

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