Import remove all trees in scenario editor patch.

http://www.tt-forums.net/viewtopic.php?f=33&t=49326

Update to current current version.
Use CMD_LANDSCAPE_CLEAR instead of CMD_CLEAR_AREA.
Whitespace, misc fixes.

src/tree_cmd.cpp

@@ -356,6 +356,24 @@ void PlaceTreesRandomly()
 	}
 }
 
+/**
+ * Remove all trees
+ *
+ * This function remove all trees on the map.
+ */
+void RemoveAllTrees()
+{
+	for(uint i = 0; i < MapSizeX(); i++) {
+		for(uint j = 0; j < MapSizeY(); j++) {
+			TileIndex tile = TileXY(i, j);
+			if(GetTileType(tile) == MP_TREES) {
+				DoCommandP(tile, 0, 0, CMD_LANDSCAPE_CLEAR | CMD_MSG(STR_ERROR_CAN_T_CLEAR_THIS_AREA), CcPlaySound10);
+			}
+		}
+	}
+}
+
+
 /**
  * Place new trees.
  *