Specialize std::swap() for Json::Value in a C++ standard compliant way

originally from pull #119

Author: datadiode

include/json/value.h

@@ -1082,6 +1082,14 @@ class JSON_API ValueIterator : public ValueIteratorBase {
 
 } // namespace Json
 
+
+namespace std {
+/// Specialize std::swap() for Json::Value.
+template<>
+inline void swap(Json::Value& a, Json::Value& b) { a.swap(b); }
+}
+
+
 #if defined(JSONCPP_DISABLE_DLL_INTERFACE_WARNING)
 #pragma warning(pop)
 #endif // if defined(JSONCPP_DISABLE_DLL_INTERFACE_WARNING)