kdd: Opt in to libxc compat xc_map_foreign_* intefaces.

kdd: Opt in to libxc compat xc_map_foreign_* intefaces.

This:

kdd-xen.c: In function 'kdd_access_physical_page':
kdd-xen.c:508:9: warning: implicit declaration of function 'xc_map_foreign_range' [-Wimplicit-function-declaration]
         map = xc_map_foreign_range(g->xc_handle,
         ^
kdd-xen.c:508:13: warning: assignment makes pointer from integer without a cast
         map = xc_map_foreign_range(g->xc_handle,
             ^

was caused by the refactoring of this functionality into
libxenforeignmemory.

Reported by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>
Tested-by: Olaf Hering <olaf@aepfle.de>