bug#35238: 27.0.50; Clarify eventp behaviour with booleans

[Stefan Monnier]

> As mentioned in a past commit[1], nil is not an event.
> Since the car of a mouse click event is considered its type,
> shouldn't (nil) also be rejected as an event?

Not sure it's worth the trouble (there are already lots of other objects
that aren't events but for which eventp returns non-nil).

> Should t be counted as an event?
>
>   (eventp t)    ; => t
>   (eventp '(t)) ; => t

Not sure if we ever generate such an event, but what would be the
benefit of rejecting it?


        Stefan