[lltx] mkluatexfontdb -> fontdbutil

[Karl Berry]

    The difference is that the default behavior has changed: 

Well, don't change it :).

    We are reluctant to break existing behavior,

I totally agree.  That would be far worse than two names.
Definitely don't do that, whatever else happens.

    Ok. What about luafontdbutil?

Fine by me.

    It will help users to see what's in their database and how to query
    it with the good name.

Sounds very good.

Thanks,
Karl