Bug 164509 Breaking API change: ColumnViewer#getItemAt(Point)
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
* @param control
	 *            the control
	 * @return the number of children
	 */
	protected abstract int getItemCount(Control control);
	/**
	 * Returns the number of child items of the given SWT item.
	 * 
	 * @param item
	 *            the item
	 * @return the number of children
	 */
	protected abstract int getItemCount(Item item);
	/**
	 * Returns the child items of the given SWT item.
	 * 
	 * @param item
	 *            the item
	 * @return the child items
	 */
	protected abstract Item[] getItems(Item item);
	/**
	 * Returns the item after the given item in the tree, or <code>null</code>
	 * if there is no next item.
	 * 
	 * @param item
	 *            the item
	 * @param includeChildren
	 *            <code>true</code> if the children are considered in
	 *            determining which item is next, and <code>false</code> if