add doxygen class definitions for native type Value classes.
#ifndef NS3_STRING_H
#define NS3_STRING_H
#include <string>
#include "attribute-helper.h"
namespace ns3 {
/**
* \class StringValue
* \brief hold variables of type string
*
* This class can be used to hold variables of type string,
* that is, either char * or std::string.
*/
ATTRIBUTE_VALUE_DEFINE_WITH_NAME (std::string, String);
ATTRIBUTE_ACCESSOR_DEFINE (String);
ATTRIBUTE_CHECKER_DEFINE (String);
} // namespace ns3
#endif /* NS3_STRING_H */