Bug 135284 [Viewers] API: need to add methods to StructuredViewer to support ViewerComparator
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/StructuredViewer.java
* @param event
	 *            a selection changed event
	 * 
	 * @see #addPostSelectionChangedListener(ISelectionChangedListener)
	 */
	protected void firePostSelectionChanged(final SelectionChangedEvent event) {
		Object[] listeners = postSelectionChangedListeners.getListeners();
		for (int i = 0; i < listeners.length; ++i) {
			final ISelectionChangedListener l = (ISelectionChangedListener) listeners[i];
			SafeRunnable.run(new SafeRunnable() {
				public void run() {
					l.selectionChanged(event);
				}
			});
		}
	}
	/**
	 * Returns the comparer to use for comparing elements, or
	 * <code>null</code> if none has been set.  If specified,
	 * the viewer uses this to compare and hash elements rather
	 * than the elements' own equals and hashCode methods.
	 *           
	 * @return the comparer to use for comparing elements or
	 *            <code>null</code>
	 */
	public IElementComparer getComparer() {
		return comparer;
	}
	/**
	 * Returns the filtered array of children of the given element. The