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.
We use getline in sim today which breaks on older systems that are
not compliant with the latest POSIX standard. For example, mingw64
for Windows omits getline so we fail to build there.
