[boost] [release] 1.63.0 now closed for new libraries and breaking changes

Hello all, The master branch is now closed for new libraries and breaking changes, and will be closing for major changes in a week (2nd Nov) and closed for the beta in two weeks (9th Nov). Also, if you're ready, you can also add your libraries' changes to the release notes at: https://github.com/boostorg/website/blob/master/feed/history/boost_1_63_0.qb... thanks, Daniel