fix `overrideDefault` method. add change `setDefaultReturn` prototype into it
when defCall is not defined and run defCall, reset defaultReturn and preReturn to undefined
rename 'defaultReturn' to 'defReturn', 'setDefaultReturn' to 'setDefReturn'
fix async mode

1. fix emit method return value when async mode is running
2. fix async mode cycle
3. `Event` add `isInAsync` param
`Event` rename `off` to `offSelf` and add `on` `off` `once` method.