(Chi) Add linref for Prep

src/chinese/CatChi.gf

@@ -89,4 +89,5 @@ concrete CatChi of Cat = CommonX - [Tense, Temp, Ant, Adv] ** open ResChi, Prelu
 
 linref
     S = linS ;
+    Prep = linPrep ;
 }

src/chinese/ResChi.gf

@@ -290,6 +290,8 @@ oper
     hasDe = advTypeHasDe at ;
     } ;
 
+  linPrep : Preposition -> Str = \p -> p.prepPre ++ p.prepPost ;
+
   advTypeHasDe : AdvType -> Bool = \at -> case at of {
       ATPoss => True ;
       _ => False