Do all pathfinding asynchronously.
Recalculate paths when the target has moved.
Fix vertex pathfinder start point heuristic, to avoid finding
zero-length paths.
When units fail to reach a resource to gather, look for another resource
of the same type.
This was SVN commit r8751.
Fix said tests for UnitAI.
Hopefully fix#647 too.
Document HFSM interface a bit.
Add Engine.DumpSimState() console command for debugging.
This was SVN commit r8681.
