[BREAKING] Change the hashset of getLineOfSight(), getTargetBlock() and ...

...getLastTwoTargetBlocks() to short

As all three of these methods currently use a HashSet that takes a Byte, it
is not possible to include block IDs greater than 127, as they would have
negative values, and thus be ignored, so we use a Short instead.

Bukkit PR: https://github.com/Bukkit/Bukkit/pull/825