Fix pathfinding and increase player path limit

The previous implementation didn't behave quite like A-* is supposed to.

After trying to figure out what's causing it and giving up,
I've reimplemented it in a straightforward manner.
Now it seems to work a lot better.

Also increases maximum player path length to 100 steps.
We still only store the first 25 steps in the save file for vanilla
compatibility.

Source/controls/plrctrls.cpp

@@ -126,9 +126,9 @@ int GetDistance(Point destination, int maxDistance)
 		return 0;
 	}
 
-	int8_t walkpath[MaxPathLength];
+	int8_t walkpath[MaxPathLengthPlayer];
 	Player &myPlayer = *MyPlayer;
-	int steps = FindPath(CanStep, [&myPlayer](Point position) { return PosOkPlayer(myPlayer, position); }, myPlayer.position.future, destination, walkpath);
+	int steps = FindPath(CanStep, [&myPlayer](Point position) { return PosOkPlayer(myPlayer, position); }, myPlayer.position.future, destination, walkpath, std::min<size_t>(maxDistance, MaxPathLengthPlayer));
 	if (steps > maxDistance)
 		return 0;