[XeTeX] not enough \XeTeXcharclass registers

[Mike "Pomax" Kamermans]

> But my first reaction to the question is to ask whether Unicode 
> character blocks are the most useful thing to map. They're rather 
> arbitrary, with things like Latin script split up across numerous 
> blocks largely due to historical accident.
>
> Mapping the Script property to char classes would seem much more 
> useful, IMO.

Yeah, there's some discussion in 
https://github.com/Pomax/ucharclasses/pull/12 to consolidate several of 
the blocks that come with "...extended..." blocks, although even then 
that might be passing the buck: Unicode seems to have picked up in terms 
of landing new versions with more and more languages (as well as 
non-languages) leading to more and more blocks, many of which count as 
new scripts, so it might simply be a matter of a few years until we 
cross the charclass limit again even if we switch to scripts rather than 
pure blocks.

- Pomax