The SQL Language Reference contains a section at the start of the manual called "What's New in the SQL Language Reference?". This lists the new features in the version, along with any deprecated features if they exist in that version. If nothing is listed, then nothing is deprecated in that version..http://docs.oracle.com/cd/E11882_01/ser ... tm#sthref3
What it wont tell you is any features that have been deprecated/removed that were never documented and supported in the first place. This is the danger in using undocumented and unsupported features. Oracle have no incentive to tell you they have been removed as you were never meant to use them anyway.
As such, you will never see a deprecation notive for WM_CONCAT, since Oracle have never supported its use outside of their won internal code.