Bug 214648 [Markers] AttributeMarkerGroupings and GroupingEntries not being cleaned up on removal
We are still leaving the references to AttributeMarkerGroupings and GroupingEntries when we unload
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/internal/MarkerSupportRegistry.java
/**
	 * The bookmarks generator.
	 */
	public static final String BOOKMARKS_GENERATOR = "org.eclipse.ui.ide.bookmarksGenerator"; 
	/**
	 * The tasks generator.
	 */
	public static final String TASKS_GENERATOR = "org.eclipse.ui.ide.tasksGenerator"; 
	/**
	 * The problems generator.
	 */
	public static final String PROBLEMS_GENERATOR = "org.eclipse.ui.ide.problemsGenerator"; 
	/**
	 * The id for the new markers view.
	 */
	public static final String MARKERS_ID = "org.eclipse.ui.ide.MarkersView"; 
	private static MarkerSupportRegistry singleton;
	
	private static Object creationLock = new Object();
	/**
	 * Get the instance of the registry.
	 * 
	 * @return MarkerSupportRegistry
	 */
	public static MarkerSupportRegistry getInstance() {
		if (singleton == null) {
			synchronized (creationLock) {
				if (singleton == null) {
					
					singleton = new MarkerSupportRegistry();