Vietnamese and Hebrew in language.dat

[Karl Berry]

    vietnamese and hebrew. Please, add them to list.

Until a hyph-utf8 update is released (the sooner the better, Arthur :),
I added the lines (r68317):

vietnamese zerohyph.tex
hebrew zerohyph.tex

to texmf-dist/tex/generic/config/language.us, which (I hope) will cause
a rebuild of the language files after the next update.

>From my reading of language.us.lua, that didn't need to be updated,
but I'm unsure.

If this causes unforeseen problems, I will revert ... --thanks, karl.