Improve error message for Global.readGlobal

Global.kics2

@@ -116,7 +116,8 @@ external_d_C_prim_readGlobal (C_Global_Pers name) _ _ = fromIO $
     case reads s of
       [(val,"")] -> return val
       _          -> throw (IOException $ "Persistent file `" ++ name ++
-                                         "' contains malformed contents")
+                                         "' contains malformed contents:\n" ++
+                                         s)
 
 external_d_C_prim_writeGlobal :: Curry_Prelude.Curry a => C_Global a -> a
                               -> Cover -> ConstStore -> Curry_Prelude.C_IO Curry_Prelude.OP_Unit