I have decided to add support for dev-lang/lua:0 because having thought quite a lot about the transition path from Lua ebuilds as they are to the new eclasses, it seems to be the most sane approach. Still, I hope this will not stay around for too long.
Nothing particularly noteworthy about LuaJIT support, possibly apart from the fact that we take advantage of it being allegedly being a drop-in replacement for lua-5.1.
