Fixing the specs on Windows

[Pepijn Van Eeckhoudt]

I've been going through the specs and up until now all failures are 
related to utime not behaving as expected on windows. I'm changing the 
specs so that they don't rely on utime but use sleeps instead. This 
makes the specs much more reliable (se linux doesn't allow mtime to be 
set in the past either IIRC), at the cost of slightly slower execution 
due to the sleeps. Is this acceptable?

Pepijn