Let apicheck check both the public API and system API.

Also "make update-api" updates both public API and system API files.

Bug: 18960664
Change-Id: I35e805816e07c8aa4deaeb84b1611923583325e1
diff --git a/core/apicheck_msg_current.txt b/core/apicheck_msg_current.txt
index 9abd381..440e7f8 100644
--- a/core/apicheck_msg_current.txt
+++ b/core/apicheck_msg_current.txt
@@ -7,7 +7,7 @@
       errors above.
 
    2) You can update current.txt by executing the following command:
-         make %UPDATE_API%
+         make update-api
 
       To submit the revised current.txt to the main Android repository,
       you will need approval.