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/udp.h b/libc/kernel/uapi/linux/udp.h
index 02e1373..3cd286b 100644
--- a/libc/kernel/uapi/linux/udp.h
+++ b/libc/kernel/uapi/linux/udp.h
@@ -29,9 +29,11 @@
 #define UDP_ENCAP 100
 #define UDP_NO_CHECK6_TX 101
 #define UDP_NO_CHECK6_RX 102
+#define UDP_SEGMENT 103
 #define UDP_ENCAP_ESPINUDP_NON_IKE 1
 #define UDP_ENCAP_ESPINUDP 2
 #define UDP_ENCAP_L2TPINUDP 3
 #define UDP_ENCAP_GTP0 4
 #define UDP_ENCAP_GTP1U 5
+#define UDP_ENCAP_RXRPC 6
 #endif