Bug 166236 [Viewers] ViewerColumn needs a dispose method
ViewerColumn adds a listener to its label provider which is never removed. We need a dispose method that removes the listener. Furthermore, if the column's label provider wraps a non-column-specific label provider, the viewer is already listening to it and the viewer column shouldn't. Must be fixed before the next I build.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ColumnViewer.java
public void activateCustomTooltips() {
		if (tooltipSupport == null) {
			tooltipSupport = new ToolTipSupport(this);
		} else {
			tooltipSupport.activate();
		}
	}
	/**
	 * Deactivate the support for custom tooltips.
	 */
	public void deactivateCustomTooltips() {
		if (tooltipSupport != null) {
			tooltipSupport.deactivate();
		}
	}
	/**
	 * Update the cached cell object with the given row and column.
	 * 
	 * @param rowItem
	 * @param column
	 * @return ViewerCell
	 */
	 ViewerCell updateCell(ViewerRow rowItem, int column) {
		cell.update(rowItem, column);
		return cell;
	}
	/**
	 * Returns the {@link Item} at the given widget-relative coordinates, or
     * <code>null</code> if there is no item at the given coordinates.
	 *