[tex-hyphen] hyphen.cfg and etex.src "stable"

[Manuel Pégourié-Gonnard]

Hi,

As far as I am concerned, the luatex-specific version of hyphen.cfg and
etex.src, the supporting luatex-hyphen.lua, as well as the format of
language.dat.lua are now stable in the following sense:

- no more changes pending on my list;
- complete documentation;
- basic tests passed (see tests/luatex).

So, this part only needs wider testing, and perhaps proof-reading by other people.

Unless I missed something, the only remaining points are:

- decide what to do with german-x, ibycus and mongolianmlc: this can be set in
language.dat.lua in either way. Of course, if the german-x team wants to provide
plain text version of their patterns, there will no longer be any hard decision
to make for german-x. I don't have a strong opinion on either of those any more,
so I'll happily let others decide :-)
- decide how language.dat.lua should be handled, and implement the chosen
mechanism. I'll open a new thread on this point for clarity.

Happy testing,
Manuel.