Update to kernel headers v4.12.3.

Test: Built angler.
Change-Id: Icbcf4fac2334de8409b049ed7a3b4c24b4e98ce9
diff --git a/libc/kernel/uapi/linux/igmp.h b/libc/kernel/uapi/linux/igmp.h
index d1ba6b1..f5d1164 100644
--- a/libc/kernel/uapi/linux/igmp.h
+++ b/libc/kernel/uapi/linux/igmp.h
@@ -42,7 +42,7 @@
 struct igmpv3_report {
   __u8 type;
   __u8 resv1;
-  __be16 csum;
+  __sum16 csum;
   __be16 resv2;
   __be16 ngrec;
   struct igmpv3_grec grec[0];
@@ -50,7 +50,7 @@
 struct igmpv3_query {
   __u8 type;
   __u8 code;
-  __be16 csum;
+  __sum16 csum;
   __be32 group;
 #ifdef __LITTLE_ENDIAN_BITFIELD
   __u8 qrv : 3, suppress : 1, resv : 4;