QCommandLinkButton resets icon on StyleChange event

With some recent patches (see https://codereview.qt-project.org/c/qt/qtbase/+/613758) the QCommandLinkButton will reset any explicitly set icon in a QCommandLinkButton once the widget is informed about a style change.

This might be a reasonable idea if during the life time of a program the user changes the style and expects default command link buttons to hav e the correct icon, but if the icon is set explicitly Qt should never touch it. 

If the user should never alter the icon of a QCommandLinkButton there should be no way to do so or at least have a note in the documentation of the QCommandLinkButton class.