The current syntax uses a pair of args
-net nic,macaddr=52:54:00:56:6c:55,vlan=3,model=pcnet,name=pcnet.0
-net user,vlan=3,name=user.0
The new syntax does not need the vlan craziness anymore, and
so has a simplified pair of args
-netdev user,id=user.0
-device pcnet,netdev=user.0,id=pcnet.0,mac=52:54:00:56:6c:55,addr=<PCI SLOT>
