Care to elaborate on how your Apache configuration is already set up for this?
This is certainly not default/standard behavior.
I have no doubt that this can be done by detecting a header for the prefetch (if there is one!) and using Apache's syntax to mod the log, AND then accounting for this in your analytics scripts ... BUT what I doubt is that this will be a simple task to push to the other 100 million server and analysis instances that I don't control.
Not to mention some of those instances will not be like the rest, and the work required to handled this will be great.