Add and use constants for the Android API levels.

Test: bionic tests still pass
Change-Id: If1b619cfc9db1d3f5d91f14f2ace71058dca0c4a
diff --git a/libc/include/netinet/in.h b/libc/include/netinet/in.h
index 3574976..10fbafa 100644
--- a/libc/include/netinet/in.h
+++ b/libc/include/netinet/in.h
@@ -47,13 +47,13 @@
 
 int bindresvport(int, struct sockaddr_in*);
 
-#if __ANDROID_API__ >= 24
+#if __ANDROID_API__ >= __ANDROID_API_N__
 extern const struct in6_addr in6addr_any __INTRODUCED_IN(24);
 extern const struct in6_addr in6addr_loopback __INTRODUCED_IN(24);
 #else
 static const struct in6_addr in6addr_any = IN6ADDR_ANY_INIT;
 static const struct in6_addr in6addr_loopback = IN6ADDR_LOOPBACK_INIT;
-#endif /* __ANDROID_API__ >= 24 */
+#endif /* __ANDROID_API__ >= __ANDROID_API_N__ */
 
 __END_DECLS