[C] Implement new skeleton AI. Fixes BUKKIT-3912

### The Issue:
Currently, Skeletons do not follow the new mob AI introduced in 1.5.

### Justification for this PR:
As CraftBukkit strives to provide an experience that is almost identical to vanilla, not following vanilla behavior is not advisable in this situation.

### PR Breakdown:
This PR changes the constructor for the EntitySkeleton's PathfinderGoalArrowAttack to the one currently used in vanilla 1.5

### JIRA Ticket:
BUKKIT-3912 - https://bukkit.atlassian.net/browse/BUKKIT-3912