[boost] 1.80.0 issue with Clang 15

I'm getting multiple reports that ContainerHash 1.80.0 doesn't compile with Clang 15, due to the following change to Config unfortunately not being part of the 1.80.0 release: https://github.com/boostorg/config/commit/f0af4a9184457939b89110795ae2d29358... Since the plans for 1.80.1 have been abandoned, it's not clear what we can do about that except probably updating the Known Issues section.