fix for boost serialization collision

Author: varunagrawal

gtsam/base/std_optional_serialization.h

@@ -56,6 +56,7 @@ namespace std { template<> struct is_trivially_move_constructible<boost::seriali
 #endif
 
 
+#if __cplusplus < 201703L
 // function specializations must be defined in the appropriate
 // namespace - boost::serialization
 namespace boost {
@@ -99,3 +100,4 @@ void serialize(Archive& ar, std::optional<T>& t, const unsigned int version) {
 }  // namespace serialization
 }  // namespace boost
 #endif
+#endif