Bug 267117 [JFace] Provide possibility for subclasses to check if a column is visible in ViewerRow
Currently this is decided by checking with width but this makes Nebula-Grid fail.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ViewerCell.java
private int columnIndex;
	private ViewerRow row;
	private Object element;
	/**
	 * Constant denoting the cell above current one (value is 1).
	 */
	public static int ABOVE = 1;
	/**
	 * Constant denoting the cell below current one (value is 2).
	 */
	public static int BELOW = 1 << 1;
	/**
	 * Constant denoting the cell to the left of the current one (value is 4).
	 */
	public static int LEFT = 1 << 2;
	/**
	 * Constant denoting the cell to the right of the current one (value is 8).
	 */
	public static int RIGHT = 1 << 3;
	/**
	 * Create a new instance of the receiver on the row.