[boost] Please merge into boostorg superproject

Please merge into boost superproject - these have passed CI and have been reviewed: https://github.com/boostorg/boost/pull/186 https://github.com/boostorg/boost/pull/181 Please decide what to do with: https://github.com/boostorg/boost/pull/39 (I can't tell if this is defunct?) https://github.com/boostorg/boost/pull/184 (do we want this in the superproject, or a submodule called boostorg/docker, or not at all?) Thanks, Jim