AMD64 port

[Matthew Dillon]

:however, most of the platform code is the same for "pc64" and "pc32".  So we need something to share this, modulo the pmap code etc.

    I suggest just copying it.  Sharing is a fine idea but in practice it
    generally creates havoc because people then make changes to the baseline
    code and don't realize that it's being shared by other architectures.

    We still have some machine-independant code that can be moved out of
    cpu/i386 and platform/pc32 and into mainline kernel sources, and we
    still have some cpu-specific code in platform/pc32 that can be moved
    to cpu/i386.

    It is also possible, theoretically, to have code in cpu/amd64 #include
    code in cpu/i386, but my strong recommendation is not to do that.  Copy
    it instead.

:>     The platforms are named differently from the architectures to avoid 
:>     the confusion that e.g. FreeBSD has when both platforms AND arcihtectures
:>     are named the same.  I don't want to call 'pc32' 'i386' when 'i386' is
:>     also the name of the cpu architecture.
:
:Yah, that is a noble goal, but still it confuses people even more :/
:
:cheers
:  simon

    It's less confusing then what FreeBSD does.  At least with DragonFly
    if you see something named 'pc32' you know exactly what it refers to.

						-Matt