* qemud/conf.c, qemud/internal.h: add dhcp config

        * qemud/qemud.c: start dnsmasq to provide dns/dhcp
        for virtual networks.

        * configure.in: add --disable-bridge-params, check
        for libsysfs and various kernel headers

        * bridge.[ch]: add code for managing bridges

        * qemud/Makefile.am: add bridge.[ch] and link against
        libsysfs if enabled.

        * qemud/conf.c: add support for bridge config.

        * qemud/internal.h: add various bridging bits

        * qemud/qemud.c: implement qemudStartNetworkDaemon()
        and qemudShutdownNetworkDaemon().

        * qemud/conf.[ch]: implement parsing and saving network
        configs.

        * qemud/driver.c: flesh out the stubs

        * qemud/internal.h: add networks list etc. to
        struct qemud_server

        * qemud/qemud.c: add qemudStartNetworkDaemon() and
        qemudShutdownNetworkDaemon() stubs.

        * qemud/qemud.c: Re-factor out qemudExec() so that it can
        be used to launch dnsmasq.

        * qemud/conf.c: don't return argc from qemudBuildCommandLine()
        as exec() doesn't need it.

        * qemud/conf.c, qemud/dispatch.c, qemud/driver.c,
          qemud/qemud.c: include autoconf's config.h

        * conf.[ch]: rename from config.[ch] so we can use
        autoconf's config.h

        * Makefile.am: update

        * driver.c, qemud.c: upd.