Enable feature interceptors for oneRow mappings

[slany]

Mapper with definition:

   abstract List<String> toValue(List<Long> rows);
   protected void myInterceptor(Long in, String value) {}

not generate method for mapping Long -> String, because this is resolvable inline in code as

   for (Long in: inList) {
     outList.add(in==null?null:in+"");
   }

Because this is generated as inline code, myInterceptor is never used.