Bug 88352 Operation supports leaks contexts via action handler
I20050315-1100 Susan, this is a different leak from the one that I reported. Test Case: 1. open text editor 2. close text editor ==> DefaultUndoManager is leaked due to undo/redo actions handlers still holding on to the context.
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/IOperationHistory.java
* @param context -
	 *            the context to be checked
	 * @return <code>true</code> if there is a redoable operation,
	 *         <code>false</code> otherwise.
	 */
	boolean canRedo(IUndoContext context);
	/**
	 * Return whether there is an undoable operation available in the given
	 * context
	 * 
	 * @param context -
	 *            the context to be checked
	 * @return <code>true</code> if there is an undoable operation,
	 *         <code>false</code> otherwise.
	 */
	boolean canUndo(IUndoContext context);
	/**
	 * Dispose of the specified context in the history. All operations that have
	 * only the given context will be disposed. References to the context in
	 * operations that have more than one context will also be removed.
	 * 
	 * @param context -
	 *            the context to be disposed
	 * @param flushUndo -
	 *            <code>true</code> if the context should be flushed from the
	 *            undo history, <code>false</code> if it should not
	 * @param flushRedo -
	 *            <code>true</code> if the context should be flushed from the
	 *            redo history, <code>false</code> if it should not.
	 *