talloc_vasprintf() has a va_list type parameter, so this type needs to
be defined (independent of the particular libc implementation).
Fixes: 63b6419d2a2d ("tools/xenstore: split out rest of live update control code") Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Juergen Gross <jgross@suse.com>