I've tried to do the bump but since we don't want to have the man pages built by the package itself but rather deliver them pre-built in a separate tarball which seems to be created by vapier I stopped at that point. The patches from 8.22 need some adjusting (especially the patch which modifies the build system to not build man pages) for which I still need to find some time working on them while vapier is away.
i added comments to the top of the 8.23 ebuild explaining how to generate the man page tarball