SMP VFS Part 2

I have updated the patch at:

http://www.chesapeake.net/~jroberson/smpffs.diff

It includes bug fixes for a handful of problems that were reported, and a
few more that I found myself.  It also unwinds giant from open(), which is
a very high risk area, but after a few days of working out bugs it seems
to be functioning quite well for me.

I did a make -j3 buildworld on a box with a lowered maxvnodes.  I also let
'stress' run for 8 loops or so until I ran into an unrelated KSE bug.  I
did some mount/unmount/single user tests as well.

Use at your own risk.  I still haven't locked quotas, so if you're using
quota, don't run with this patch.

Thanks,
Jeff