o Fix module ref counts so that you can actually unload dm-mod

 o Fix module ref counts so that you can actually unload dm-mod
   N.B. This means that you have to take very great care in the event that
   you want to access the dcache tree from in kernel

 o Added extra field to allow out of memory conditions to result in the
   correct error code. (This hasn't received a lot of testing...)

I've ditched the final project (which would have cleared my whole list)
since its got other complications which I don't have time to fix right
now. Still as Meatloaf says, two out of three ain't bad!