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/dns_resolver.h b/libc/kernel/uapi/linux/dns_resolver.h
new file mode 100644
index 0000000..21cb5c0
--- /dev/null
+++ b/libc/kernel/uapi/linux/dns_resolver.h
@@ -0,0 +1,78 @@
+/****************************************************************************
+ ****************************************************************************
+ ***
+ ***   This header was automatically generated from a Linux kernel header
+ ***   of the same name, to make information necessary for userspace to
+ ***   call into the kernel available to libc.  It contains only constants,
+ ***   structures, and macros generated from the original header, and thus,
+ ***   contains no copyrightable information.
+ ***
+ ***   To edit the content of this header, modify the corresponding
+ ***   source file (e.g. under external/kernel-headers/original/) then
+ ***   run bionic/libc/kernel/tools/update_all.py
+ ***
+ ***   Any manual change here will be lost the next time this script will
+ ***   be run. You've been warned!
+ ***
+ ****************************************************************************
+ ****************************************************************************/
+#ifndef _UAPI_LINUX_DNS_RESOLVER_H
+#define _UAPI_LINUX_DNS_RESOLVER_H
+#include <linux/types.h>
+enum dns_payload_content_type {
+  DNS_PAYLOAD_IS_SERVER_LIST = 0,
+};
+enum dns_payload_address_type {
+  DNS_ADDRESS_IS_IPV4 = 0,
+  DNS_ADDRESS_IS_IPV6 = 1,
+};
+enum dns_payload_protocol_type {
+  DNS_SERVER_PROTOCOL_UNSPECIFIED = 0,
+  DNS_SERVER_PROTOCOL_UDP = 1,
+  DNS_SERVER_PROTOCOL_TCP = 2,
+};
+enum dns_record_source {
+  DNS_RECORD_UNAVAILABLE = 0,
+  DNS_RECORD_FROM_CONFIG = 1,
+  DNS_RECORD_FROM_DNS_A = 2,
+  DNS_RECORD_FROM_DNS_AFSDB = 3,
+  DNS_RECORD_FROM_DNS_SRV = 4,
+  DNS_RECORD_FROM_NSS = 5,
+  NR__dns_record_source
+};
+enum dns_lookup_status {
+  DNS_LOOKUP_NOT_DONE = 0,
+  DNS_LOOKUP_GOOD = 1,
+  DNS_LOOKUP_GOOD_WITH_BAD = 2,
+  DNS_LOOKUP_BAD = 3,
+  DNS_LOOKUP_GOT_NOT_FOUND = 4,
+  DNS_LOOKUP_GOT_LOCAL_FAILURE = 5,
+  DNS_LOOKUP_GOT_TEMP_FAILURE = 6,
+  DNS_LOOKUP_GOT_NS_FAILURE = 7,
+  NR__dns_lookup_status
+};
+struct dns_payload_header {
+  __u8 zero;
+  __u8 content;
+  __u8 version;
+} __packed;
+struct dns_server_list_v1_header {
+  struct dns_payload_header hdr;
+  __u8 source;
+  __u8 status;
+  __u8 nr_servers;
+} __packed;
+struct dns_server_list_v1_server {
+  __u16 name_len;
+  __u16 priority;
+  __u16 weight;
+  __u16 port;
+  __u8 source;
+  __u8 status;
+  __u8 protocol;
+  __u8 nr_addrs;
+} __packed;
+struct dns_server_list_v1_address {
+  __u8 address_type;
+} __packed;
+#endif