Update to v4.19 kernel headers.

Test: Builds and boots.
Change-Id: I99a9ed79666e143b47f02ca4e59eed94f69b7e4a
(cherry picked from commit a981e2e52e2e95a65fa9c9b6fb16dcb4c83dd576)
diff --git a/libc/kernel/uapi/asm-x86/asm/unistd_64.h b/libc/kernel/uapi/asm-x86/asm/unistd_64.h
index 3cde166..a118200 100644
--- a/libc/kernel/uapi/asm-x86/asm/unistd_64.h
+++ b/libc/kernel/uapi/asm-x86/asm/unistd_64.h
@@ -351,4 +351,6 @@
 #define __NR_pkey_alloc 330
 #define __NR_pkey_free 331
 #define __NR_statx 332
+#define __NR_io_pgetevents 333
+#define __NR_rseq 334
 #endif