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-generic/siginfo.h b/libc/kernel/uapi/asm-generic/siginfo.h
index af3d98e..166193b 100644
--- a/libc/kernel/uapi/asm-generic/siginfo.h
+++ b/libc/kernel/uapi/asm-generic/siginfo.h
@@ -194,7 +194,8 @@
 #define TRAP_TRACE 2
 #define TRAP_BRANCH 3
 #define TRAP_HWBKPT 4
-#define NSIGTRAP 4
+#define TRAP_UNK 5
+#define NSIGTRAP 5
 #define CLD_EXITED 1
 #define CLD_KILLED 2
 #define CLD_DUMPED 3