Use FLEXIBLE_ARRAY_MEMBER in some more places.

Fix a batch of structs that are only visible within individual .c files.

Michael Paquier

src/backend/postmaster/checkpointer.c

@@ -130,7 +130,7 @@ typedef struct
 
 	int			num_requests;	/* current # of requests */
 	int			max_requests;	/* allocated array size */
-	CheckpointerRequest requests[1];	/* VARIABLE LENGTH ARRAY */
+	CheckpointerRequest requests[FLEXIBLE_ARRAY_MEMBER];
 } CheckpointerShmemStruct;
 
 static CheckpointerShmemStruct *CheckpointerShmem;