Adding virtio_net.h from Linux. There are following changes different from Linux:
* "class" field in struct virtio_net_ctrl_hdr renamed to class_of_command
so the file could be compiled with C++ file
* Empty field macs removed from struct virtio_net_ctrl_mac (not used anyway in Windows)
* VIRTIO_NET_CTRL_GUEST_OFFLOADS control is added
* Struct packing set Windows style
Signed-off-by: Yan Vugenfirer <[email protected]>
