Path finding: Make MC and EC unsigned everywhere
While I don't expect this to fix path finding overflow alain_bkr saw on https://osdn.net/projects/freeciv/ticket/46286#comment:12505:46286:1679918727 , this should be a step to the right direction, and potentially already fix some other cases.
As path_finding.h comments say, MC and EC should always be positive. However, current code treats them as signed ints almost everywhere. Turn them to unsigned instead.
Mostly untested patch, but still a commit candidate (I'll test while it's in review).
While I don't expect this to fix path finding overflow alain_bkr saw on https://osdn.net/projects/freeciv/ticket/46286#comment:12505:46286:1679918727 , this should be a step to the right direction, and potentially already fix some other cases.
As path_finding.h comments say, MC and EC should always be positive. However, current code treats them as signed ints almost everywhere. Turn them to unsigned instead.