Send root process to SCrashed if it dies while unbooted

This one is a bit tricky: Sometimes when running under bundle exec
under some ruby projects, the root process will fail to start up while
it's getting restarted. In that case, root process tree node wouldn't
budge from SUnbooted without the ability to get restarted even if its
dependencies changed).

This change makes the babysitter process watch out for
unexpected (that is, non-"signal 9") crashes and nudges it into
SCrashed if the crash happened in SUnbooted.