util/StringPointer: add typedef reference_type

src/util/AllocatedString.hxx

@@ -44,6 +44,8 @@ template<typename T=char>
 class AllocatedString {
 public:
 	typedef typename StringPointer<T>::value_type value_type;
+	typedef typename StringPointer<T>::reference_type reference_type;
+	typedef typename StringPointer<T>::const_reference_type const_reference_type;
 	typedef typename StringPointer<T>::pointer_type pointer_type;
 	typedef typename StringPointer<T>::const_pointer_type const_pointer_type;
 

src/util/StringPointer.hxx

@@ -37,6 +37,8 @@ template<typename T=char>
 class StringPointer {
 public:
 	typedef T value_type;
+	typedef T &reference_type;
+	typedef const T &const_reference_type;
 	typedef T *pointer_type;
 	typedef const T *const_pointer_type;