Allow lists to contain list references.

Allow lists to contain list references by expanding any references to
the items in the list, before storing the list items in
state.lists. Prior to this change, some list references might be
expanded simply due to the way the list items were iterated over in
compile_macro/compile_filter.

userspace/falco/lua/rule_loader.lua

@@ -137,7 +137,21 @@ function load_rules(filename)
       elseif (v['list']) then
 	 -- list items are represented in yaml as a native list, so no
 	 -- parsing necessary
-	 state.lists[v['list']] = v['items']
+	 local items = {}
+
+	 -- List items may be references to other lists, so go through
+	 -- the items and expand any references to the items in the list
+	 for i, item in ipairs(v['items']) do
+	    if (state.lists[item] == nil) then
+	       items[#items+1] = item
+	    else
+	       for i, exp_item in ipairs(state.lists[item]) do
+		  items[#items+1] = exp_item
+	       end
+	    end
+	 end
+
+	 state.lists[v['list']] = items
 
       else -- rule