Update to v4.19 kernel headers.

Test: Builds and boots.
Change-Id: I99a9ed79666e143b47f02ca4e59eed94f69b7e4a
(cherry picked from commit a981e2e52e2e95a65fa9c9b6fb16dcb4c83dd576)
diff --git a/libc/kernel/uapi/linux/tipc_config.h b/libc/kernel/uapi/linux/tipc_config.h
index c52f5ff..a371e37 100644
--- a/libc/kernel/uapi/linux/tipc_config.h
+++ b/libc/kernel/uapi/linux/tipc_config.h
@@ -90,6 +90,7 @@
 #define TIPC_MIN_LINK_WIN 16
 #define TIPC_DEF_LINK_WIN 50
 #define TIPC_MAX_LINK_WIN 8191
+#define TIPC_DEF_LINK_UDP_MTU 14000
 struct tipc_node_info {
   __be32 addr;
   __be32 up;