Performing a dev build against the latest version of Qt failed
because of some deprecated members. They have been replaced
according to the Qt documentation.
Further, Q_OS_MACOS is now the only macro available to identify a
machine running macOS, the others are now deprecated.
See https://doc.qt.io/qt-5/qtglobal.html#Q_OS_OSX and
https://doc.qt.io/qt-5/qtglobal.html#Q_OS_MAC.