Bug 137442 [DataBinding] (C)ComboObservableValue should bind to selection index
3.2M6: I propose to extend (C)ComboObservableValue such that they could bind int.class values for pure selection changes of an otherwise immutable combo content. E.g. swtbinding allows such binding to an index holder and the class would attach as SelectionListener where it asks the combo for its selection index. Maybe the corresponding property should be assigned to SWTProperties.SELECTION_INDEX. Similar arguments could be given for corresponding extensions for SWT-List widgets.
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/swt/SWTObservables.java
* @throws IllegalArgumentException
	 *             if <code>control</code> type is unsupported
	 */
	public static ISWTObservableValue observeSelection(Control control) {
		if (control instanceof Spinner) {
			return new SpinnerObservableValue((Spinner) control,
					SWTProperties.SELECTION);
		} else if (control instanceof Button) {
			return new ButtonObservableValue((Button) control);
		} else if (control instanceof Combo) {
			return new ComboObservableValue((Combo) control,
					SWTProperties.SELECTION);
		} else if (control instanceof CCombo) {
			return new CComboObservableValue((CCombo) control,
					SWTProperties.SELECTION);
		} else if (control instanceof List) {
			return new ListObservableValue((List) control);
		} else if (control instanceof Scale) {
			return new ScaleObservableValue((Scale) control,
					SWTProperties.SELECTION);
		}
		throw new IllegalArgumentException(
				"Widget [" + control.getClass().getName() + "] is not supported."); 
	}
	/**
	 * Returns an observable observing the minimum attribute of the provided
	 * <code>control</code>. The supported types are:
	 * <ul>
	 * <li>org.eclipse.swt.widgets.Spinner</li>
	 * <li>org.eclipse.swt.widgets.Scale</li>