In normal use, GNU `yes` does unbuffered IO on stdout. However, it does use buffered IO for --help and --version messages; it sets atexit(close_stdout) to cove

In normal use, GNU `yes` does unbuffered IO on stdout. However, it does use buffered IO for --help and --version messages; it sets atexit(close_stdout) to cover both of those cases at once, rather than handling them both separately.