luatex-1.17.0 update

[Karl Berry]

FYI: some issues have been found in luatex (obscure ways to work around
some security features; thanks to Max Chernoff).  Luigi has committed
fixes to the sources, and we are rebuilding now. The new luatex version
is 1.17.0. All four luatex binaries (luatex luahbtex luajitex luajithbtex)
are affected. The different platforms will come in as the respective
builders have time; so far, x86_64-linux and *-netbsd have been updated.

The change that's most likely to be noticeable is that the socket
library is now disabled by default; a new option --socket enables it, as
well as --shell-escape (not --shell-restricted). In addition, the mime
library is now always available, and new functions os.socketsleep and
os.socketgettime are also always available. I will put a more detailed
summary at https://tug.org/texlive/bugs.html after the binaries are
committed.

The new binaries do not, so far as I know, even require a .fmt rebuild,
though tlmgr will make that happen anyway as a matter of course with a
normal installation.

Good luck to us all,
Karl