• Allow IO::Async::Notifier to be used as a non-principle mixin class
  
• Provide Notifier->loop accessor
  
• Added (still-experimental) Notifier debug features
  
• Deleted various deprecated features:
  
  • Notifier to Handle upgrade
    
  • Loop->enable_childmanager, Loop->disable_childmanager
    
• Print deprecation warnings on Loop->detach_code, Loop->detach_child
  
• Minor improvements to LoopTests