loop, to use signals properly. There are two copies of this code; one
uses kvm and the other uses sysctls. One copy had been updated to use
sigset_t and sigsuspend; the other was using vintage sigpause(). Sync
up the code so both use sigpause. Also, use sig_atomic_t, and block
SIGALRM when not waiting for it to avoid a small and unlikely but real
race.
Since the non-modernized copy of the code *had* for some been
modernized to use setitimer instead of just alarm(), propagate that
change to the other copy.
These copies could share more logic than they do.
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