SMP FFS Part 3

[Jeff Roberson]

This patch removes Giant from every file related syscall.  It fixes all
known bugs except for one which Peter Holm has seen after very long
periods of extreme load, and a nfs netbooting problem that I haven't yet
looked in to.  I can buildworld -j3 for hours on my dual opteron without
issues.  I hope to fix the remaining problems in a day or two.

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

Cheers,
Jeff