[1.6.x] Fixed #20005 -- Documented that Oracle databases need execute permission on SYS.DBMS_LOB.

Thanks jafula for the suggestion.

Backport of a86ecc80a2 from master

docs/ref/databases.txt

@@ -683,6 +683,14 @@ To run Django's test suite, the user needs these *additional* privileges:
 * CONNECT WITH ADMIN OPTION
 * RESOURCE WITH ADMIN OPTION
 
+The Oracle database backend uses the ``SYS.DBMS_LOB`` package, so your user
+will require execute permissions on it. It's normally accessible to all users
+by default, but in case it is not, you'll need to grant permissions like so:
+
+.. code-block:: sql
+
+    GRANT EXECUTE ON SYS.DBMS_LOB TO user;
+
 Connecting to the database
 --------------------------