[libvirt] [PATCH 0 of 3] LXC network interface support

This set is actually authored by Dave Leskovec. He is moving on to some other work and I will be working this into the tree. I have made a few changes to this, mostly to allow this code to compile out if the proper kernel and userspace support is not present. I am submitting it as an RFC because the required kernel patches are not yet upstream (even in -mm) and there are some missing userspace patches to iproute2 as well. I expect there to be quite a few comments and suggestions about the veth.c patch, so I wanted to go ahead and get that started while we wait for upstream to catch up. Comments appreciated!