[development] Object caching

[Karoly Negyesi]

> I don't understand how you can have a contributed alternate bootstrap?   
> If cache.inc would allow for avoiding avoid the Drupal bootstrap I'd be  
> interested.
>
> Kieran

a) Drupal configuration is loaded from settings.php. If herein we find  
$conf['page_cache_fastpath'] = TRUE then the following happens:
b) cache.inc is loaded
c) page_cache_fastpath is called
d) Drupal exits.

That avoids pretty much all of Drupal. This was added to the cache.inc  
patch to let you serve the files as fast as possible. I added this with an  
eye on the file caching patch.