[libvirt] [PATCH 0/6] (informational) conf support for <interface type='hostdev'>

This series of patches enhances the domain parser/formatter code to support a sort of "intelligent hostdev", i.e. PCI passthrough where device-type specific initialization is done prior to assigning the device to the guest, in particular to allow setting the MAC address and do 802.1QbX setup for network devices. Rather than adding all of the device-type specific config to <hostdev>, I accomplish this through adding a new type of <interface> element, type='hostdev'. When an interface is type='hostdev' the following is changed: * in the toplevel device, the managed attribute can be specified (with identical results as when it's specified in a <hostdev> * The <source> element can specify a pci address or usb address, just as can be done in <hostdev>. One notable difference is that the type of the address is specified directly in the source <address> element, rather than as an attribute of the toplevel device (that's how it's done for <hostdev>, but for <interface>, the toplevel element's type attribute is already used). These patches include only the parser/formatter, test (for domainschematest, and qemuxml2xmltest only), and doc changes; they still need to be hooked into the domain's device lists (a type=hostdev interface will reside in both the interface list (for configuration and memory management) and hostdev list (for attach/detach, and tracking of which devices are assigned)). I don't intend to push these patches until that part is also done, but some other people are doing work that depends on the changes to config format and data structures, so I'm sending these patches now both to unblock them, as well as to get feedback from everyone else on what needs to be changed. The first 4 patches are just setup for the real new code - they reorder and refactor existing code to allow greater re-use of existing code and easier plugin of the new code. Patch 5/6 is just a couple of lines, and patch 6/6 provides the new functionality.