[tex-hyphen] luatex-hyphen & TL

[Manuel Pégourié-Gonnard]

Hi,

I finally got to implementing an extension of execute AddHyphen
directive and related things for generating a language.dat.lua in TL.
(This r18379 in case you want to review it; Norbert, your comments are
welcome.)

It is documented in TeXlive::TLPSRC and tlmgr's man page (section
GENERATE), but here is a summary:
- execute AddHyphen has been extended with fours parameters:
  - txtpatt and txthyph for the name of the files with patterns and
    exceptions in plain text;
  - luaspecial for the special paramater in language.dat.lua (see
    hyphen-luatex.pdf for details about that one) (must be quoted if
    it contains spaces, can always be quoted);
  - databases: comma-separated list, by default dat,def, changed to
    dat,def,lua if the line contains one of the three variables above.
    This indicates the files in which this entry should be used
    (language.{dat,def,dat.lua}). It is currently useless thanks to the
    default values, but may be useful in the future when people want to
    release patterns to be loaded only with Luatex.
- tlmgr generate language now generates language.dat.lua, and accepts
  this as an argument. Also, language.dat.lua is regenerated after
  changes in packages containing an execute AddHyphen directive.
- just like other language files, a local file language-local.dat.lua
  can be used to disable, modifiy or add entries.

I also made two minor changes to luatex-hyphen, the only notable being
that patterns and hyphenation may be nil or '' to indicate that there
are no pattens (or exceptions) for this language.

Now, the only remaining item that I can think of is to update the
various tlpsrc files. I don't know how the files in TL/.../tlpsrc in
texhyphen are maintained (manually, generated, ...), so I'll let you do
it, unless you want some help. Then I think everything will be ready for
inclusion in TL.

Of course, as the patterns providers, it's up to you to put what you
want in the tlpsrc files, like disabling ibycus and mongolian-mlc. Other
patterns authors (like german-x) are not expected to provide tlpsrc
files: we'll ask them what to do and write the tlpsrc file ourselves.

As always, comments welcome :-)

Manuel.