Versioning of the file format

[Svante Schubert <Svante.Schubert@Sun.COM>]

As promised in the call, to ask back for potential heavy problems when 
using versioning.
Currently our development nor our user experience see no such problems 
in case of introducing versioning.

I also got the feedback, which I have to agree on as the editor, that if 
we specify a versioning in the proposal, the workflow descriptions (e.g. 
increment the revision number by one) do not belong in the normative 
section of the file format specification. The Accessibility SC does it 
the same way and adds informative sections describing this.

I guess everybody agrees on this, I just wanted to make it clear from 
the beginning.

Svante.