Bug 123316 [Undo] - API BEHAVIOR - should always place a successfully undone/redone op on the redo/undo history
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/IOperationHistory.java
* of the operation is subject to approval by any registered
	 * {@link IOperationApprover} before it is attempted.
	 * </p>
	 * 
	 * @param context
	 *            the context to be undone
	 * @param monitor
	 *            the progress monitor to be used for the undo, or
	 *            <code>null</code> if no progress monitor is provided.
	 * @param info
	 *            the IAdaptable (or <code>null</code>) provided by the
	 *            caller in order to supply UI information for prompting the
	 *            user if necessary. When this parameter is not
	 *            <code>null</code>, it should minimally contain an adapter
	 *            for the org.eclipse.swt.widgets.Shell.class.
	 * 
	 * @return the IStatus indicating whether the undo succeeded.
	 * 
	 * <p>
	 * The severity code in the returned status describes whether the operation
	 * succeeded and whether it remains in the history. <code>OK</code>
	 * severity indicates that the undo operation was successful. The operation
	 * will be placed on the redo history, provided it can be redone (answers
	 * <code>true</code> to {@link IUndoableOperation#canRedo()}). Listeners
	 * will receive the <code>UNDONE</code> notification.
	 * </p>
	 * <p>
	 * Other severity codes (<code>CANCEL</code>, <code>ERROR</code>,
	 * <code>INFO</code>, etc.) are not specifically interpreted by the
	 * history. The operation will remain in the history and the returned status