Bug 89971 [Viewers] Viewers that use IViewerLabelProvider do too many instanceof checks
M6 Checking our viewer the calls to buildLabel are doing too many instanceof checks. As a result certain viewers (such as the table viewer) are twice as slow as they were in 3.0 due to these checks. I have written some performance suites to test the Table, Tree, List and Combo viewers. Table and Tree have this issue.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TableViewer.java
* @param position
	 *            a 0-based position relative to the model, or -1 to indicate
	 *            the last position
	 */
	public void insert(Object element, int position) {
		tableViewerImpl.applyEditorValue();
		if (getSorter() != null || hasFilters()) {
			add(element);
			return;
		}
		if (position == -1)
			position = table.getItemCount();
		
		createItem(element,position);
	}
	/*
	 *  (non-Javadoc)
	 * @see org.eclipse.jface.viewers.StructuredViewer#internalRefresh(java.lang.Object)
	 */
	protected void internalRefresh(Object element) {
		internalRefresh(element, true);
	}
	/*
	 *  (non-Javadoc)
	 * @see org.eclipse.jface.viewers.StructuredViewer#internalRefresh(java.lang.Object, boolean)
	 */
	protected void internalRefresh(Object element, boolean updateLabels) {
		tableViewerImpl.applyEditorValue();
		if (element == null || equals(element, getRoot())) {
			if(virtualManager == null)