title: std::mutex :: when the lock acquired thread gets killed what would happen to other waiting threads with respect to std::mutex locks
body: <p>Multiple threads are trying to access a critical area and assume we use <code>std::mutex</code> to lock it.
  Now one of the thread acquired the lock and after sometime if it gets killed .. what would be the system behavior? Similar to pthread mutex robust do we have anything for <code>std::mutex</code>?</p>