Time keeping Issues with the low-resolution TSC timecounter

[Matt]

>> Hmm...  GPF seems to be related to unclean %rcx.  Can you please
>> try the attached patch?  Please note you have to rebuild kernel
>> from scratch because this is a header file change.  It may not fix
>> "hang", though.  Please let me know.
> It is just committed at r223796.
>
> JK
>

This issue is resolved for me. Thanks Jung-uk! It's a far nicer fix than 
clobbering out TSC-low :).

Matt