Extend object access hook framework to support arguments, and DROP.

This allows loadable modules to get control at drop time, perhaps for the
purpose of performing additional security checks or to log the event.
The initial purpose of this code is to support sepgsql, but other
applications should be possible as well.

KaiGai Kohei, reviewed by me.

src/backend/commands/proclang.c

@@ -428,7 +428,7 @@ create_proc_lang(const char *languageName, bool replace,
 
 	/* Post creation hook for new procedural language */
 	InvokeObjectAccessHook(OAT_POST_CREATE,
-						   LanguageRelationId, myself.objectId, 0);
+						   LanguageRelationId, myself.objectId, 0, NULL);
 
 	heap_close(rel, RowExclusiveLock);
 }