* qemud/conf.c: add support for connecting a qemu
        guest to a bridge using a tap device in order to
        connect it to a virtual network.

        * qemud/internal.h: add <interface type="network">
        config and track tapfds so as to not close them
        on exec.

        * qemud/qemud.c: don't close tapfds on exec and
        disconnect the iface when the guest shuts down.