icon cache scriplet guideline update

[Bill Nottingham]

Jason L Tibbitts III (tibbs at math.uh.edu) said: 
> BN> You seriously want a script to be handling per-transaction state
> BN> of the updater that's running it? That sounds like a very wrong
> BN> solution.
> 
> Well, If you can point out where I said that, I'll surely correct
> myself because that certainly wasn't what I intended.

Matthias mentioned how this doesn't solve the 'regenerates the cache
many many times' issue, and you stated that 'the xdg script could
solve that.'

Bill