make virtual_integral_iterator compatible with c++ standard library

alib2std/src/extensions/foreach.hpp

@@ -297,6 +297,16 @@ class virtual_pointer_to_integer {
 	IntegralType m_data;
 public:
+	typedef IntegralType value_type;
+
+	typedef std::ptrdiff_t difference_type;
+
+	typedef IntegralType * pointer;
+
+	typedef IntegralType reference;
+
+	typedef std::bidirectional_iterator_tag iterator_category;
+
 	/**
 	 * \brief
 	 * Constructor of the virtual pointer class.