busybox

fix read_cmdline API and a small buglet where "[comm]" may be too narrow

function                                             old     new   delta
func_args                                             25      26      +1
read_cmdline                                         119     114      -5
display_process_list                                1462    1447     -15
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(add/remove: 0/0 grow/shrink: 1/2 up/down: 1/-20)             Total: -19 bytes

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