File IO basically done

You can do this:
cat '#Z' <-- get the entries
ls -l '#Z'
cat '#Z/regressctl'
echo v > '#Z/regressctl'
cat '#Z/malloc'

and so on.

I think there's an issue in here with either kfs or this stuff. I'm seeing
occasional issues but can't track them down to this code. That said, when
I grew busybox I started getting malloc arena corruption.

I think we need a function to preen the arena, which could be called at any
point but could most usefully be called at end of a system call.

Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>