fix for CVE-2016-2858 doesn't build with qemu-xen enabled
    Unsanitised guest input in libxl device handling code
    	[XSA-175, CVE-2016-4962] (#1342132)
    Unsanitised driver domain input in libxl device handling
    	[XSA-178, CVE-2016-4963] (#1342131)
    arm: Host crash caused by VMID exhaust [XSA-181] (#1342530)
    Qemu: display: vmsvga: out-of-bounds read in vmsvga_fifo_read_raw() routine
    	[CVE-2016-4454] (#1340741)
    Qemu: display: vmsvga: infinite loop in vmsvga_fifo_run() routine
    	[CVE-2016-4453] (#1340746)
    Qemu: scsi: esp: OOB write when using non-DMA mode in get_cmd
    	[CVE-2016-5238] (#1341931)