[libvirt] libvirt-gconfig patches

Hi, This is the 2nd version of my libvirt-gconfig patches. I think I have addressed all of the issues that were raised (or told why I didn't address them). If I missed anything, just let me know. Some of the patches have been split/merged after the review so the series look a bit different from the first one even if the content is the same. One notable change is that I dropped the chardev classes for now since I need to go back to the drawing board a bit for these Christophe