FreeBSD-5 boot code almost ported

[Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>]

    I'm about 80% of the way through porting the FreeBSD-5 boot code.
    Basically the entire /usr/src/sys/boot from FreeBSD-5.

    It compiles!  I haven't tried running it yet :-)... but I had to
    bring in the new linker set code which means that I have to 
    incorporate Peter Wemm's 2001/06/13 03:58:40 PST commit in sys
    from FreeBSD-5 which converts all the kernel linker set mechanisms
    (e.g. this is what SYSCTL uses to collect all the sysctl records
    together).  That is straightforward but is likely going to take me
    into tomorrow.

    But then I'll be able to commit the whole mess and we will have the
    latest and greatest boot code from FreeBSD-5, capable of loading 
    ELF64 kernels.

						-Matt