merge vm_version_x86_{32,64}.hpp

[Christian Thalinger]

On Mon, 2009-02-23 at 07:29 -0500, Paul Hohensee wrote:
> Imo, the #ifdef's are ok in this case because they're quite limited.
> 
> Vladimir set prefetch distances based on experiment.  The difference
> between 320 and 384 is a single cache line.  It seems to me that 32
> and 64-bit would be the same because it's the same hardware, except
> that it may be that 64-bit code is faster than 32-bit code, thus would
> require a slightly greater prefetch distance.
> 
> 32-bit doesn't use the Prefetchxxx switches because there's no common
> prefetch instruction for 32-bit that can be used in C++ code.  #ifdef is
> ok here.

Paul, thank you for the explanation.  Last question: should I use the
_LP64 or AMD64 define?

-- Christian