Fix tooltips on e.g. Ubuntu.

CupPlugin/src/de/tum/in/www2/cupplugin/widgets/TooltipBase.java

@@ -107,6 +107,8 @@ public abstract class TooltipBase {
 		popup.setBackground(background);
 		this.scrolled.setBackground(background);
 		this.label.setBackground(background);
+		this.label.setForeground(display.getSystemColor (SWT.COLOR_INFO_FOREGROUND));
+
 		
 		popup.setSize(10, 10);
 	}