emit resize signal when altering the iconbar mode

Otherwise the iconbar would be capped when showing more (eg. all instead
of iconified) windows

src/IconbarTool.cc

@@ -352,6 +352,8 @@ void IconbarTool::setMode(string mode) {
     }
     reset();
 
+    resizeSig().emit();
+
     // unlock graphics update
     m_icon_container.setUpdateLock(false);
     m_icon_container.update();