Bug 167170 [Markers] Need to check for duplicate filter names
M3 It is currently possible to enter duplicate filter names
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/internal/DialogMarkerFilter.java
String categoryName = MarkerSupportRegistry.getInstance()
					.getCategory(markerType.getId());
			if (categoryName == null) {
				elements.add(new MarkerTypeNode(markerType));
			} else {
				MarkerCategory category;
				if (categories.containsKey(categoryName)) {
					category = (MarkerCategory) categories.get(categoryName);
				} else {
					category = new MarkerCategory(categoryName);
					categories.put(categoryName, category);
					elements.add(category);
				}
				MarkerTypeNode node = new MarkerTypeNode(markerType);
				category.add(node);
			}
			MarkerType[] subTypes = ((MarkerType) obj).getSubtypes();
			for (int j = 0; j < subTypes.length; j++) {
				buildTypeTree(elements, subTypes[j], categories);
			}
		}
	}
	/**
	 * Grey check the parent if required
	 * 
	 * @param element
	 * @param checked
	 */
	private void setParentCheckState(Object element, boolean checked) {
		Object parent = typesContentProvider.getParent(element);