Per buildfarm, the "#ifdef F_SETFD" removed in that commit actually
is needed on Windows, because fcntl() isn't available at all on that
platform, unless using Cygwin.  We could perhaps spell it more like
"#ifdef HAVE_FCNTL", or "#ifndef WIN32", but it's not clear that
those choices are better.

It does seem that we don't need the bogus manual definition of
FD_CLOEXEC, though, so keep that change.

Discussion: https://postgr.es/m/26254.1492805635@sss.pgh.pa.us