Changes for version 1.90
- Maintainer change and tooling update
 - Fix to prevent delete_observer() from breaking observer references
 - No more weakening of observer refs
 - Proper inside-out implementation, including DESTROY and a CLONE for thread safety (please note the documentation section on DESTROY)
 - No more debug code (but debug-related functions and methods kept for backcompat)
 
Modules
Allow other classes and objects to respond to events in yours