Update to v4.20.1 kernel headers.

This includes one manual change:

In the file bionic/libc/kernel/uapi/linux/in.h, the macro IN_BADCLASS
was not definied correctly. Change the macro from:

  #define IN_BADCLASS(a) ((((long int) (a)) == 0xffffffff)

to:

  #define IN_BADCLASS(a) (((long int) (a)) == (long int)0xffffffff)

This change is being pushed to the upstream kernels.

Test: Builds and boots.
Change-Id: Ia304773a9dc6789b34d9769d73742384d6afb571
Merged-In: Ia304773a9dc6789b34d9769d73742384d6afb571
(cherry picked from commit 967fb01cce73591281e7804e2c0fa9f83b618f5b)
diff --git a/libc/kernel/uapi/linux/in6.h b/libc/kernel/uapi/linux/in6.h
index 9da111c..3627f52 100644
--- a/libc/kernel/uapi/linux/in6.h
+++ b/libc/kernel/uapi/linux/in6.h
@@ -132,6 +132,7 @@
 #define IPV6_V6ONLY 26
 #define IPV6_JOIN_ANYCAST 27
 #define IPV6_LEAVE_ANYCAST 28
+#define IPV6_MULTICAST_ALL 29
 #define IPV6_PMTUDISC_DONT 0
 #define IPV6_PMTUDISC_WANT 1
 #define IPV6_PMTUDISC_DO 2