sed: code shrink

sed: code shrink

function                                             old     new   delta
get_next_line                                        246     250      +4
sed_main                                             671     662      -9
add_input_file                                        47       -     -47
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 1/1 up/down: 4/-56)             Total: -52 bytes

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