Qt::AA_DontShowIconsInMenus should defer to the style

In GNOME/X11 environments, there's a hardcoded check in QApplication for a specific GNOME config setting ("/desktop/gnome/interface/menus_have_icons") during initialization. If this setting is disabled, the Qt::AA_DontShowIconsInMenus attribute is set, globally disabling icons in menus (by default).

Although applications that want to blend in with a GNOME desktop environment want to match the user's preference, those with highly customized styles may require more specific behavior. In our case, important icons simply disappeared when we upgraded to a newer desktop environment that had a different default value for this GNOME setting.

The workaround is simple: force the Qt::AA_DontShowIconsInMenus attribute to true after initializing the application.

But really, it seems wrong for this to be a global attribute in the first place; this should be driven by the style, like virtually every other aspect of a menu's visual appearance.