Add Vehicle to on_player_driving_changed_state

[zackman0010]

I am currently trying to create a new PvP scenario, one that relies heavily on walls. I would like to be able to detect if a player is trying to jump over a wall by using the fact vehicles teleport players on entry/exit. Currently, my only option is to do a search around the player for any entity where type=="car", but this may not be accurate if there are multiple vehicles around the player. If the vehicle the player was entering/exiting would be included in the on_player_driving_state event, that would make use cases such as this much easier.

[Rseding91]

Added for 0.16.