dual head support (SDL_VIDEO_FULLSCREEN_HEAD) for Qt and SDL2
dual head support for Qt reworked / --fullscreen for Qt / fullscreen top most
dual head support for Qt reworked / --fullscreen for Qt / fullscreen top most
amendments for: global variable 'fullscreenCLI'/move on top timer/Qt fullscreen code
merged with upstream / amended SDL2 multi monitor support
rebase
Merge pull request #6937 from beaumanvienna/retrorig-pl1

dual head support (SDL_VIDEO_FULLSCREEN_HEAD) for Qt and SDL2