Add type_traits include. PR #533 used std::underlying_type to make the MemoryOrder

enum work with C++ 20 but apparently some older gcc instance still want the type_traits
include that defines the underlying_type template.

Author: Bret McGuire

src/atomic/atomic_std.hpp

@@ -18,6 +18,7 @@
 #define DATASTAX_INTERNAL_ATOMIC_STD_HPP
 
 #include <atomic>
+#include <type_traits>
 
 namespace datastax { namespace internal {