[libvirt] [PATCHv4 0/2] vnc/spice listen address as a network name

This is the latest reincarnation of this patch series: https://www.redhat.com/archives/libvir-list/2011-July/msg01717.html In the previous version, I had created a new subelement of <graphics>, called <listen>, and placed all listen address and port attributes there. After discussion on the list and in IRC with Dan Berrange and Eric Blake, I became convinced that was overdoing things, and that really only the address or network name should be in the <listen> element, but that port/tlsPort/autoport should stay put. This version removes all changes to port-related attributes, paring it down to just the listen address (and the new listen network) attribute. This greatly simplifies the patch, so new review of it should be easier. Based on Eric's review, the nwe version tries to be more concise about what is accepted, what is ignored, and what is rejected in the XML, both by the parser and by the RNG. (since there is less to deal with, this is also easier.) Having a single port value but multiple addresses does create some potential future restrictions, which we can deal with an eliminate later if they become problematic. In particular, each graphics device will have only a single port, but could have multiple listen addresses; in this case, all the listen addresses would have to listen on the same port. (This isn't a problem right now, because all of our drivers can only listen on a single address anyway). (Note to Eric: I did consider putting the switch to helper functions into its own patch, but after removing all the ports from <listen>, the number of helper functions (and thus the number of changes created by switching to using them, has been reduced considerably, so the gain wouldn't be as much. (also, it's very late, and I'd like to get some sleep tonight :-)