Add versioning information to symbols.

Bug: http://b/28178111
Change-Id: I46bf95accd819f4521afb1173d8badcc5e9df31c
diff --git a/libc/include/android/set_abort_message.h b/libc/include/android/set_abort_message.h
index 4b3d82b..aebedba 100644
--- a/libc/include/android/set_abort_message.h
+++ b/libc/include/android/set_abort_message.h
@@ -33,7 +33,7 @@
 
 __BEGIN_DECLS
 
-void android_set_abort_message(const char* msg);
+void android_set_abort_message(const char* msg) __INTRODUCED_IN(21);
 
 __END_DECLS