Implement the new virtio sockets device for host<->guest communication
using the Sockets API.  Most of the work is done in a vhost kernel
driver so that virtio-vsock can hook into the AF_VSOCK address family.
The QEMU vhost-vsock device handles configuration and live migration
while the rx/tx happens in the vhost_vsock.ko Linux kernel driver.

The vsock device must be given a CID (host-wide unique address):

  # qemu -device vhost-vsock-pci,id=vhost-vsock-pci0,guest-cid=3 ...

For more information see:
http://qemu-project.org/Features/VirtioVsock

[Endianness fixes and virtio-ccw support by Claudio Imbrenda
<imbrenda@linux.vnet.ibm.com>]
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
[mst: rebase to master]
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>