Bug 203838 [Markers] [Markers] clicking on column headers does not sort table
I20070918 Clicking on any of the column headers does not sort based on the relevant column.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/provisional/views/markers/CachedMarkerBuilder.java
* Return the {@link MarkerGroup} being used for categorisation.
	 * 
	 * @return {@link MarkerGroup} or <code>null</code>.
	 */
	MarkerGroup getCategoryGroup() {
		return generator.getCategoryGroup();
	}
	/**
	 * Return the elements in the adapter.
	 * 
	 * @return Object[]
	 */
	public MarkerItem[] getElements() {
		if (currentMap == null) {
			scheduleMarkerUpdate();
			building = true;
		}
		if (building) {
			return MarkerSupportInternalUtilities.EMPTY_MARKER_ITEM_ARRAY;
		}
		if (generator.isShowingHierarchy() && categories != null) {
			return categories;
		}
		return currentMap.toArray();
	}
	/**
	 * Return the generator for the receiver.
	 * 
	 * @return MarkerContentGenerator
	 */