This updates gnulib to a relatively recent commit. Most of this was
done by the gnulib import script; the only change I made was to
update-gnulib.sh.
Tested on x86-64 Fedora 34. I also did a mingw cross build.
Some sim ports use these to provide networking functionality via the
dv-sockser module or via direct emulation for a few ports.
Gdb seems to build just fine still too.