Bug 170668 [DataBinding] [Patch] Add SWTObservables.observeTooltipText()
Adds support for binding to SWT Control TooltipText property.
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/swt/SWTObservables.java
return new ComboObservableValue(combo, SWTProperties.TEXT);
	}
	/**
	 * @param combo
	 * @return
	 */
	public static ISWTObservableValue observeSelection(Combo combo) {
		return new ComboObservableValue(combo, SWTProperties.SELECTION);
	}
	/**
	 * @param combo
	 * @return
	 */
	public static IObservableList observeItems(Combo combo) {
		return new ComboObservableList(combo);
	}
	/**
	 * @param combo
	 * @param event
	 * @return
	 */
	public static ISWTObservableValue observeText(CCombo combo) {
		return new CComboObservableValue(combo, SWTProperties.TEXT);
	}
	/**
	 * @param combo
	 * @return
	 */
	public static ISWTObservableValue observeSelection(CCombo combo) {
		return new CComboObservableValue(combo, SWTProperties.SELECTION);