Workaround a lack of std::function support in QThreadPool < 5.15
QThreadPool::start(std::function) was only introduced in Qt 5.15. This adds a workaround (basically importing the class from Qt 5.15) for earlier Qt versions.
QThreadPool::start(std::function) was only introduced in Qt 5.15. This adds a workaround (basically importing the class from Qt 5.15) for earlier Qt versions.