Bug 89020 [Undo] Operation throws assertion failure if undo limit is set to 0
I20050324-0800 Unfortunately existing clients of text's undo manager were allowed to set any number without failing. This is no longer possible: an assertion failure occurrs if the limit is smaller than 1. I will add code on my side that will handle the negative numbers but the operation history must allow 0.
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/IOperationHistory.java
* "Undo" menu.
	 * 
	 * @param context -
	 *            the context for the undo
	 * @return the operation to be undone or <code>null</code> if there is no
	 *         operation available. There is no guarantee that the available
	 *         operation is valid for the undo.
	 */
	IUndoableOperation getUndoOperation(IUndoContext context);
	/**
	 * Redo the most recently undone operation in the given context
	 * 
	 * @param context -
	 *            the context to be redone
	 * @param monitor -
	 *            the progress monitor to be used for the redo, or <code>null</code> if no
	 *            progress monitor is provided.
	 * @param info -
	 *            the IAdaptable (or <code>null</code>) provided by the
	 *            caller containing additional information. When this API is
	 *            called from the UI, callers can use this to provide additional
	 *            info for prompting the user. If an IAdaptable is provided,
	 *            callers are encourated to provide an adapter for the
	 *            org.eclipse.swt.widgets.Shell.class.
	 * @return the IStatus indicating whether the redo succeeded.
	 * 
	 * 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 redo operation was successful and that the
	 * operation has been placed on the undo history. Listeners will receive the