<netinet/in6.h>: don't require <string.h>.

Using __builtin_memcmp() rather than memcmp() means the caller doesn't need to have also included <string.h>.

Change-Id: I1d37bd9295de3a478ae3082ddbdc1ec482fbd039

Author: enh-google

libc/include/netinet/in6.h

@@ -89,7 +89,7 @@
   (IN6_IS_ADDR_MULTICAST(a) && (IPV6_ADDR_MC_SCOPE(a) == IPV6_ADDR_SCOPE_GLOBAL))
 
 #define IN6_ARE_ADDR_EQUAL(a, b) \
-  (memcmp(&(a)->s6_addr[0], &(b)->s6_addr[0], sizeof(struct in6_addr)) == 0)
+  (__builtin_memcmp(&(a)->s6_addr[0], &(b)->s6_addr[0], sizeof(struct in6_addr)) == 0)
 
 #define INET6_ADDRSTRLEN 46