Fix undefined reference to 'close_used_without_including_unistd_h'

Fix undefined reference to 'close_used_without_including_unistd_h'

Found while trying to cross-compile libvirt on Fedora 12 for Windows.
gnulib redefines 'close' to 'close_used_without_including_unistd_h'
in sys/socket.h if winsock2.h is present and unistd.h has not been
included before sys/socket.h. Reorder some includes to fix this.