Use a label point for the general representative point for polygons

(Skipping the iteration to find one that is as far as possible from
the borders)

This makes the labels look better in many cases (like France at z1)
but unfortunately ripples into changing the sequence of polygons in
many tests, so the diff is big.

tile.cpp

@@ -2105,7 +2105,7 @@ long long write_tile(FILE *geoms, std::atomic<long long> *geompos_in, char *meta
 				}
 
 				sf.t = VT_POINT;
-				sf.geometry = polygon_to_anchor(sf.geometry);
+				sf.geometry = polygon_to_anchor(sf.geometry, true);
 			}
 
 			if (sf.geometry.size() > 0) {