Skeleton cannot damage player who is at the same position

This relates to MC-12845 however fixing that issue would very likely not fix this one as this here is an AI problem.

When you stand at the same position as a Skeleton it will try to shoot you but never hits you. The problem that it cannot hit you is probably not fixable as it could hit itself then. However it should maybe try to get away from the player instead to be able to shoot him again.