o Minor bugfixes (shutdown, libevent, memory safety):
    - Avoid use-after-free bugs when shutting down, by making sure that we
      shut down libevent only after shutting down all of its users. We
      believe these are harmless in practice, since they only occur on the
      shutdown path, and do not involve any attacker-controlled data. Fixes
      bug 30629; bugfix on 0.4.1.1-alpha.