Hi Sebastian, What exactly are you trying to do? What does it have to do with xmodmap? I would like to try and help, but I've read through this thread and it's very unclear as to what you're trying to do. Compile StumpWM on Ubuntu?
Either way. I think IRC (#stumpwm) would be a better place to get help. People will be able to offer advice in real-time and you won't have to wait for days in between compile errors.