Document that mixing old/new forms in QML Connections causes new form to not work

(Not sure if this is a bug, or a need for updated documentation. Also please edit component(s) as required).

The Connections QML type can accept signals declared with the old form (onSignal: {...}) or the new form (function onSignal() {...}).

If BOTH are used in the same connections block, those declared with the new form (function) do not work.

All files necessary to build demo app are attached. Change the comments in the Connections block in Window.qml to test different combinations of old/new form.