+** Modification of events from a running event handler is always safe.
+** Deleting an already deleted event is always safe.
+** For any event type, it is possible to ask whether it is active (added to the mainloop) or not: <<mainloop:fun_hook_is_active,`hook_is_active()`>> and friends.
+** A new mainloop front-end for asynchronous <<mainloop:recordio,record-based I/O>> has been added.