[tlbuild] LuaMetaTeX for TeX Live

[Karl Berry]

    at some point in the future worked with autotools 2.71 as well.)

I do use autoconf-2.71, as documented in tlbuild and reported at the top
of every generated configure script.

IMHO those "deprecations" were a bad idea and should not have been
done. Therefore I am not spending my time dealing with them. If you
specify -Wno-obsolete when you call autoconf, as the TL reautoconf
script does, they will not show up.

If someone else wants to spend time fiddling with the Autoconf code to
placate the warnings, fine by me. -k