Quick notes on running MacOS X, NetBSD and Windows 7 together under KVM on Linux

As a reminder for myself, mostly:
- Only Mavericks, Yosemite is not yet working under KVM.
- KVM SLiRP networking does not work with MacOS X, bridging is hard to setup for wireless networks so it is better to use NAT versions of qemu-ifup and qemu-ifdown.
- It looks so cool on screenshots