While being at it: create a new inet_dgram_opts() function for udp setup,
so udp can handle IPv6 now.

new cmd line syntax:
    -chardev udp,id=name,host=remotehost,port=remoteport,\
	localaddr=bindaddr,localport=bindport

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>