Merged Pathfinding code cleanup from Hercules
(https://github.com/HerculesWS/Hercules/commit/78028c8)
* This fixes a problem where units sometimes walk diagonally through a wall server-sided; there should be less client desync now (but it might not be perfect yet)
* I kept the rAthena specific option path_blown_halt
* Special thanks to piotrhalaczkiewicz for the original implementation and aleos for helping me with the merge