Add new `supported_node_facedir` group and apply it to item frames

This group acts similarly to `supported_node`: it checks whether the
node behind is airlike (in which case the node is dropped as an item).
This change should fix item frames not placing on chests and similar
blocks, as reported by Bear123 on Discord.

mods/CORE/mcl_attached/init.lua

@@ -94,5 +94,16 @@ function minetest.check_single_for_falling(pos)
 		end
 	end
 
+	if get_item_group(node.name, "supported_node_facedir") ~= 0 then
+		local dir = facedir_to_dir(node.param2)
+		if dir then
+			local def = registered_nodes[get_node(vector.add(pos, dir)).name]
+			if def and def.drawtype == "airlike" then
+				drop_attached_node(pos)
+				return true
+			end
+		end
+	end
+
 	return false
 end

mods/ITEMS/mcl_itemframes/item_frames_API.lua

@@ -638,7 +638,7 @@ function mcl_itemframes.create_base_definitions()
 		paramtype = "light",
 		paramtype2 = "facedir",
 		sunlight_propagates = true,
-		groups = { dig_immediate = 3, deco_block = 1, dig_by_piston = 1, container = 1, attached_node_facedir = 1 },
+		groups = { dig_immediate = 3, deco_block = 1, dig_by_piston = 1, container = 1, supported_node_facedir = 1 },
 		sounds = mcl_sounds.node_sound_defaults(),
 		node_placement_prediction = "",