[lltx] implementation of btex .. etex in luamplib

[Élie Roux]

Dear Kim,

> I am planning to upload a package for Korean to CTAN.  Among the files
> in the package, two files attached as a zip file in this mail are not
> just for Hangul but might be used also for other languages or math
> equations.  They are substitutes for luamplib, enabling btex .. etex
> for typesetting non-ascii characters in mplibcode environment.  I
> suggest here to adopt them to current luamplib package, so that I can
> remove them from my package to be uploaded to CTAN.

This sounds good, they will be easily adapted to luamplib. When I'll 
merge them, will you have time to test them before I upload it to ctan? 
I'll push them (today certainly) on 
https://github.com/lualatex/luamplib. Or do you have tests already?

Thank you,
-- 
Elie