This allows qemu-ga to function as a Windows service:

 - to install the service (will auto-start on boot):
     qemu-ga --service install
 - to start the service:
     net start qemu-ga
 - to stop the service:
     net stop qemu-ga
 - to uninstall service:
     qemu-ga --service uninstall

Original patch by Gal Hammer <ghammer@redhat.com>