[annotation] allow-none for vfuncs
Submitted by Tomeu Vizoso
Link to original bug (#616873)
Description
Some classes have vfuncs that are not required to be implemented by subclasses. Others will crash if there isn't an implementation because don't check if there's one.
Also, there are interfaces that can be partially implemented.
If introspection bindings could know which vfuncs are safe to be left unimplemented, they could enforce that the other vfuncs are implemented so that crashes can be avoided.