kdb: add rdmsr and wrmsr commands for i386

[Mitch Bradley]

> Also, would it make sense to coordinate the order of the high and low
> dwords with the order they are specified with 'wrmsr'?  
> I don't think it matters which order (lo-hi hi-lo) you use - The AMD
> debuggers use hi:lo, and Mitch uses lo:hi -  as long as you pick one
> and stay consistant, we'll be fine.
>
>   
Actually, Mitch uses hi.lo .  Examples:

ok 1808 .msr
25fff002.10f00000.
ok 400000ef.c00fffff. 51010020 msr!


Mitch