GetPathLength: add optional depth parameter

This is also exposed by the PathFinder defcore entry.

docs/sdk/script/fn/GetPathLength.xml

@@ -30,6 +30,11 @@
           <name>endy</name>
           <desc>Y coordinate of end position. Always global coordinate.</desc>
         </param>
+        <param>
+          <type>int</type>
+          <name>depth</name>
+          <desc>Determines search depth of the pathfinder algorithm (range from 1 - 10 with default 1). Warning: higher values may slow down the game. See also the PathFinder entry in the <emlink href="definition/properties.html">DefCore</emlink>.</desc>
+        </param>
       </params>
     </syntax>
     <desc>Searches for a path from start point to end point using the pathfinding algorithm as used by clonks and returns the length of the found path. Returns <code>nil</code> if no path was found.</desc>

src/game/C4GameScript.cpp

@@ -2019,12 +2019,15 @@ private:
 	PathInfo *pPathInfo;
 };
 
-static Nillable<long> FnGetPathLength(C4PropList * _this, long iFromX, long iFromY, long iToX, long iToY)
+static Nillable<long> FnGetPathLength(C4PropList * _this, long iFromX, long iFromY, long iToX, long iToY, long iLevel)
 {
 	PathInfo PathInfo;
 	PathInfo.ilx = iFromX;
 	PathInfo.ily = iFromY;
 	PathInfo.ilen = 0;
+	if (!iLevel)
+		iLevel = 1;
+	Game.PathFinder.SetLevel(iLevel);
 	if (!Game.PathFinder.Find(iFromX, iFromY, iToX, iToY, SumPathLength(&PathInfo)))
 		return C4Void();
 	return PathInfo.ilen + Distance(PathInfo.ilx, PathInfo.ily, iToX, iToY);