Update to v4.15 kernel headers.

Test: Compiles, boots bullhead/hikey960.
Change-Id: I118beb8b6cac0881b1270f9bf6981959297a41a8
diff --git a/libc/kernel/uapi/linux/ip6_tunnel.h b/libc/kernel/uapi/linux/ip6_tunnel.h
index b7df956..ba59235 100644
--- a/libc/kernel/uapi/linux/ip6_tunnel.h
+++ b/libc/kernel/uapi/linux/ip6_tunnel.h
@@ -29,6 +29,7 @@
 #define IP6_TNL_F_MIP6_DEV 0x8
 #define IP6_TNL_F_RCV_DSCP_COPY 0x10
 #define IP6_TNL_F_USE_ORIG_FWMARK 0x20
+#define IP6_TNL_F_ALLOW_LOCAL_REMOTE 0x40
 struct ip6_tnl_parm {
   char name[IFNAMSIZ];
   int link;