With Qt5 on Mac, the tool buttons in the browser window toolbar appear flat...

With Qt5 on Mac, the tool buttons in the browser window toolbar appear flat similar to a label.  The background color is the same as the toolbar's background color and there is no border around the tool button.  Added function WuQtUtilities::setToolButtonStyleForQt5Mac(QToolButton*) that uses a style sheet to lighten the tool buttons background and add a slightly darker border around the button.