[boost] [optional] Top level bad_optional_access.hpp

Hi, I've noticed a new top-level header boost/bad_optional_access.hpp. It wasn't present in 1.55, so it is a recent development. AFAIK, top level headers are discouraged, all library specific headers, except the "include all" header, should be inside the library directory. Am I correct? If so, could this header be moved inside boost/optional?