[boost] [release] Master branch is now open for bug fixes

Hi, The master branch is now open for bug fixes, test and documentation changes, but please follow the policy described in: https://github.com/boostorg/wiki/wiki/Releases%3A-Beta-Merge-Policy The next deadline: On April 1st, the master branch closes for all changes. As always, the calendar is at https://www.boost.org/calendar — The release managers