hush: fix login shell's signal handling; add -l option so that it's easier to test

function                                             old     new   delta
hush_main                                            958    1001     +43
install_special_sighandlers                           47      52      +5
packed_usage                                       28752   28741     -11
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(add/remove: 0/0 grow/shrink: 2/1 up/down: 48/-11)             Total: 37 bytes

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