It's really easy, just build K-Meleon againt M18 and it should compile fine. I used to test it with M18 but released K-Meleon with M17 as M18 is not yet a milestone.
So the downloadable binary's built against M17 API, right? I'm running a nightly Mozilla here, which I guess has a bit different of an API seeing that if I try to run k-meleon, it instantly crashes on "module <unknown>".
Would anyone be able to spare the time to compile a binary linked with M18 and make it available? This way it will be easier to test gecko without loading all the chrome stuff that Mozilla loads. It is really quite hard to get compile tools if you don't program windows for a living...