Update issue with QMouseOverEvent in widgets/calculator example on Mac

Update issue with QMouseOverEvent in widgets/calculator example on Mac.

1. Go to <qt4.4.3>\examples\widgets\calculator
2. Build the "calculator" example
3. Run the "calculator" example
4. From the System MenuBar , show the calculator menu and move mouse over the calculator menu and keep on moving mouse (without clicking) towards "calculator" application window
5) once you reach over the calculator application window, press mouse button and drag it over all the button

If one click and hold the mouse button, and moves it around the widget, all buttons will be pressed, but not released untill clicked properly.