Add and use constants for the Android API levels.

Test: bionic tests still pass
Change-Id: If1b619cfc9db1d3f5d91f14f2ace71058dca0c4a
diff --git a/libc/include/android/legacy_sys_wait_inlines.h b/libc/include/android/legacy_sys_wait_inlines.h
index 63343eb..1124f8e 100644
--- a/libc/include/android/legacy_sys_wait_inlines.h
+++ b/libc/include/android/legacy_sys_wait_inlines.h
@@ -34,7 +34,7 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
-#if __ANDROID_API__ < 18
+#if __ANDROID_API__ < __ANDROID_API_J_MR2__
 
 __BEGIN_DECLS
 
@@ -44,6 +44,6 @@
 
 __END_DECLS
 
-#endif /* __ANDROID_API__ < 18 */
+#endif /* __ANDROID_API__ < __ANDROID_API_J_MR2__ */
 
 #endif /* _ANDROID_LEGACY_SYS_WAIT_INLINES_H_ */