kobov4 exists solely because there's a dedicated TC for it,
but we don't distribute binaries for it (it doesn't differ enough from
kobo, and experience has taught us that this kind of split was not a
great idea (e.g., kindle5 vs. kindlepw2)).
kobov5 targets a massively updated userland, and requires further
changes, including to the delivery mechanism, so it very much warrants a
dedicated package (re: #12401)
