Remove <netinet/icmp6.h> ni_* macros.

glibc doesn't have these, and they prevent ping from building out of
the box because it assumes it can define them.

Bug: 9671560
Change-Id: I815f2a9c4fd96a0ea2952eb5a71ddf51e0763660
diff --git a/libc/include/netinet/icmp6.h b/libc/include/netinet/icmp6.h
index 0ecc2e5..6625712 100644
--- a/libc/include/netinet/icmp6.h
+++ b/libc/include/netinet/icmp6.h
@@ -390,11 +390,15 @@
 	/* could be followed by reply data */
 } __packed;
 
+/*
+ * BEGIN android-removed: glibc doesn't have these, and external/ping declares them itself.
 #define ni_type		icmp6_ni_hdr.icmp6_type
 #define ni_code		icmp6_ni_hdr.icmp6_code
 #define ni_cksum	icmp6_ni_hdr.icmp6_cksum
 #define ni_qtype	icmp6_ni_hdr.icmp6_data16[0]
 #define ni_flags	icmp6_ni_hdr.icmp6_data16[1]
+ * END android-removed
+ */
 
 #define NI_QTYPE_NOOP		0 /* NOOP  */
 #define NI_QTYPE_SUPTYPES	1 /* Supported Qtypes */