hush: do not reset sighaldlers after fork - instead, prevent them from doing any...

hush: do not reset sighaldlers after fork - instead, prevent them from doing any harm
 if they will be called. saves many sigaction calls on every fork.

function                                             old     new   delta
hush_main                                            887     971     +84
sigexit                                               54      65     +11
run_list                                            2006    2001      -5
maybe_set_sighandler                                  76      50     -26
set_fatal_sighandler                                 186       -    -186
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(add/remove: 0/1 grow/shrink: 2/2 up/down: 95/-217)          Total: -122 bytes