bc: eliminate BC_STATUS_INPUT_EOF

bc: eliminate BC_STATUS_INPUT_EOF

function                                             old     new   delta
fflush_and_check                                       -      36     +36
bc_num_a                                             445     456     +11
bc_num_ulong                                          85      95     +10
bc_vm_run                                           1978    1984      +6
bc_num_s                                             246     252      +6
bc_err_msgs                                          192     188      -4
quit                                                  38      32      -6
bc_vm_process                                        139     132      -7
bc_program_reset                                     172     159     -13
bc_parse_create                                      192     175     -17
bc_read_line                                         349     311     -38
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 4/6 up/down: 69/-85)            Total: -16 bytes
   text	   data	    bss	    dec	    hex	filename
 987844	    485	   7296	 995625	  f3129	busybox_old
 987828	    485	   7296	 995609	  f3119	busybox_unstripped

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