tor/changes/bug4457

  o Minor bugfixes:
    - Initialize Libevent with the EVENT_BASE_FLAG_NOLOCK flag enabled, so
      that it doesn't attempt to allocate a socketpair. This could cause
      some problems on windows systems with overzealous firewalls. Fix for
      bug 4457; workaround for Libevent versions 2.0.1-alpha through
      2.0.15-stable.

    - Detect failure to initialize Libevent. Better detection for bug 4457.