Add dry-colored grass/fern variants

mods/ITEMS/mcl_core/nodes_trees.lua

@@ -112,7 +112,7 @@ local register_sapling = function(subname, description, longdesc, texture, selbo
 			local node_below = minetest.get_node_or_nil({x=pos.x,y=pos.y-1,z=pos.z})
 			if not node_below then return false end
 			local nn = node_below.name
-			return (nn=="mcl_core:dirt_with_grass" or nn=="mcl_core:dirt_with_grass_snow" or
+			return ((minetest.get_item_group(nn, "grass_block") == 1) or
 					nn=="mcl_core:podzol" or nn=="mcl_core:podzol_snow" or
 					nn=="mcl_core:dirt")
 		end),