[Unison-hackers] Upgrade the unison stable version

[Benjamin Pierce]

> Another suggestion: Document the fact that Unison is not safe to use
> with removable media without a backup preference. And/Or: Recommend,
> that the user should place the unison directory (with his archive  
> files)
> on the removable disk itself.

This is not a sufficient fix: If the removable device goes offline  
*while* Unison is checking for updates (but after it has read the  
archive), unfortunate behavior will still result.

     - Benjamin