Add vioif driver to OmniOS for better networking under qemu-kvm

```
Shows vioif working onder latest stable release + onu from illumos-omnios with these changes
root@omnios-vioif:/root# modinfo | grep vioif
182 fffffffff7d02000   36b0 264   1  vioif (VirtIO ethernet driver)
root@omnios-vioif:/root# dladm show-phys
LINK         MEDIA                STATE      SPEED  DUPLEX    DEVICE
vioif0       Ethernet             up         1000   full      vioif0
root@omnios-vioif:/root# dladm show-link
LINK        CLASS     MTU    STATE    BRIDGE     OVER
vioif0      phys      1500   up       --         --
root@omnios-vioif:/root# ipadm show-addr
ADDROBJ           TYPE     STATE        ADDR
lo0/v4            static   ok           127.0.0.1/8
vioif0/dhcp       dhcp     ok           172.16.15.170/24
lo0/v6            static   ok           ::1/128
```

screenshot: http://sjorge.sinners.be/illumos/omnios/vioif-booted.PNG
build logs: http://sjorge.sinners.be/illumos/omnios/vioif-buildlogs.tar.bz2