Add ext_lfb_base to dom0_vga_console_info, from recent Xen. We know if it's
present or not by checking dom0.info_size

branches: 1.1.1;
Initial revision

Import Xen public headers version 4.11.1

Release tag: RELEASE-4-11-1

git log of the freeze is as follows:

commit 96cbd0893f783997caaf117e897d5fa8f2dc7b5f
Author: Jan Beulich <jbeulich@suse.com>
Date: Thu Nov 29 15:04:11 2018 +0100

update Xen version to 4.11.1