HAMMER filesystem update

[Matthew Dillon]

    I am going to start committing bits and pieces of the HAMMER filesystem
    over the next two months.  Note that the filesystem will not be
    operational until we get closer to the 2.0 release in December so
    these bits and pieces will not be tied into buildworld/buildkernel until
    then.

    I am making good progress and I believe it will be beta quality by the
    release.  It took nearly the whole year to come up with a workable
    design.  I thought I had it at the beginning of the year but I kept
    running into issues and had to redesign the thing several times
    since then.  I finally had to compromise a bit on the efficiency of the
    backup/mirroring data stream and the filesystem relies a lot more on
    heuristics and background balancing then I want it to, but other
    then that the design will meet all the goals that were laid out at
    the beginning of the year.

    I will post the design document the implementation is being based on in
    a moment.

						-Matt