[libvirt] [PATCH 0/5] Interface Config public APIs and remote stubs

These 5 patches contain the public virInterface*() API definition, the local plumbing, and the RPC glue. The test driver and real driver are still TBI, but having this in will allow other people to work on related stuff. Other things still needed: python/java bindings cli commands in virsh I'm sure lots of other things I don't know about yet. Note that I have added a couple things to the API that I previously didn't realize were needed (virInterfaceRef and virInterfaceFree - I had figured the client side would just pass around a cookie, not actually have storage associated with it).