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/sysctl.h b/libc/kernel/uapi/linux/sysctl.h
index eb6e61f..24d8362 100644
--- a/libc/kernel/uapi/linux/sysctl.h
+++ b/libc/kernel/uapi/linux/sysctl.h
@@ -491,7 +491,8 @@
   __NET_IPV6_MAX
 };
 enum {
-  NET_IPV6_ICMP_RATELIMIT = 1
+  NET_IPV6_ICMP_RATELIMIT = 1,
+  NET_IPV6_ICMP_ECHO_IGNORE_ALL = 2
 };
 enum {
   NET_NEIGH_MCAST_SOLICIT = 1,