[luatex] Support for Thai in LuaTeX

[Arthur Reutenauer]

> A very interesting question! Next thing on my todolist is to handle
> tibetan. It seems to have the same kind of difficulty, and the rules
> for end of lines could be summarized as follows: you can end a line
> only on a space (which is rare) or after a certain character
> (tshegs, U0F0B). How could it be possible to handle this?

  Your problem is quite different, Élie: you simply need to insert break
opportunities after each tsek.

	Arthur