[XeTeX] disabling xetex's default classes

[Michiel Kamermans]

Jonathan Kew wrote:
> Well, if your package overwrites the classes of all the characters, 
> then 0 through 3 will be empty! I'm not sure what else you need?
My bad, I had forgotten to use a new counter for the default and it was 
generating wacky results, which made it look like classes 0 through 4 
were still active =)

> It should be present in the xetex and xelatex formats (defined via the 
> xetex.ini and xelatex.ini files that are used to build these). So I'd 
> recommend you use this to allocate your classes, rather than a 
> separate (and potentially conflicting) allocator.
>
> (I guess you'd have to check for its existence if you want your 
> package to work on older setups, and provide your own definition if 
> it's missing.)
Alrightio, I'll have a look there then.

- Mike