[boost] [iterator][range] Old breaking change in develop.

Hi, There's an old breaking change to iterator_facade in iterator's develop branch, which is apparently needed for iterator_range (although it seems to have got by without it): https://github.com/boostorg/iterator/commit/512298cb5cf4b7ca5e8000f41bb39bda... Please can someone who cares about it decide if that's something that should be released, and if they think it is, take responsibility for it (documentation, release notes, support, etc.). If not, I think it should be reverted. Daniel