[PATCH] Allow using system luajit

[Karl Berry]

    Subject: [PATCH] Allow using system luajit

Thanks much for the patch. I installed it (r73471 and 2), since the
changes do no apparent harm if the new option isn't used. At least I was
still able to build in the usual way.

Administrivia: I put myself in as the "copyright" holder of the new
files for consistency, although if you want to be listed, no problem. It
makes no practical difference. I did list you in the ChangeLog entries.

    This does currently *not* result in a successful build (tested with
    openresty luajit 2.1 as packaged in Debian and Alpine); some more
    work is required for that, such as not relying on lua_rawlen or the
    internal lj_arch.h header.

That will be up to Luigi, or you, or some other contributor.
I forwarded your msg to Luigi.

    It has a second purpose though: Allowing texlive to be built without
    luajit (configure --without-luajit), which is a reasonable stop-gap
    solution for architectures to which luajit has not been ported yet.

Yes, that's a good thing.

Thanks again. -k