Add a kernel log buffer

This is handy when your laptop keeps overrunning your screen.

cat '#c/kmesg' > '#r/xyz' to put it somewhere.

If you just cat it, it never ends. Sorry. I tried.

Signed-off-by: Ronald G. Minnich <rminnich@google.com>
Attempts to fix krefs in pgrp/fgrp

For IDs, we don't want krefs.  For some of the stuff, we don't even have
init methods yet.  And we don't want to call closefgrp.  But if we do,
it'll be slightly better.