added Question.AdvIAdv and correcponding entry of mkIAdv in API

src/romance/QuestionRomance.gf

@@ -93,6 +93,7 @@ incomplete concrete QuestionRomance of Question =
       n = n
       } ;
 
+    AdvIAdv i a = {s = i.s ++ a.s} ;
 
     CompIAdv a = {s = \\_  => a.s} ;