[boost] [Serialization] boost/strong_typedef.hpp vs. boost/serialization/strong_typedef.hpp

Hi folks, Does anyone know why boost/strong_typedef.hpp still exists with real content? Several years back, the version in the trunk was stubbed out: http://svn.boost.org/svn/boost/trunk/boost/strong_typedef.hpp but this change has not made it into any release. The version in serialization, however, is still being updated. Sincerely, Jonathan Jones