Boost.Bimap fork that incorporates Pull Request #11 <https://github.com/boostorg/bimap/pull/11>, Pull Request #12 <https://github.com/boostorg/bimap/pull/12>, Pull Request #13 <https://github.com/boostorg/bimap/pull/13>, and Pull Request #14 <https://github.com/boostorg/bimap/pull/14>.