Rotation option for spill_item_stack

[sparr]

spill_item_stack spills in a deterministic order around the target location. That makes its behavior inconsistent when applied in rotated neighborhoods.

Example: Spill an item just south of a belt and the first spill will end up on the belt. Rotate the whole coordinate system so that you're spilling just north of the belt and the spilled item goes even farther north rather than on the belt.

Request: at least, add an "orientation" option to spill_item_stack that does 90/180/270 degree rotation of the overflow spill locations.