[luatex] Support for Thai in LuaTeX

[Arthur Reutenauer]

> With a quick search, I saw "linebreak_filter" callback in LuaTeX reference.
> is that relevant to the problem?

  Yes, that's one of the callbacks you can use to hook word segmentation
into TeX's flow, and that's the one I would recommend.

>                                  or using external filter is already
> acceptable?

  You should be the one answering this question, as you're probably the
only one on this list who's going to typeset Thai with LuaTeX: do you
want to continue using an external filter?  LuaTeX provides ways to
avoid that entirely, but of course that needs some additional code to be
written.

  In any case, LuaTeX is essentially compatible with pdfTeX, so whatever
worked with pdfTeX should work with LuaTeX too.

	Arthur