add an option to close sessions as soon as child exits.
Maybe it should be a CONFIG option. OTOH, maybe it should be always on,
as it mimics, say, getty's behaviour.
function old new delta
handle_sigchld - 49 +49
telnetd_main 1312 1355 +43
.rodata 123429 123466 +37
packed_usage 22770 22806 +36
make_new_session 525 532 +7
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 4/0 up/down: 172/0) Total: 172 bytes
text data bss dec hex filename
676285 2538 12104 690927 a8aef busybox_old
676421 2538 12104 691063 a8b77 busybox_unstripped
2450c450ab