I removed dbus-x11
I needed to remove pulseaudio to be able to remove dbus - after that the N900 went black and rebooted
Then tried apt-get install -f , apt-get suggested to autoremove a bunch of packages so I executed apt-get autoremove and tried apt-get install -f again, but it failed (without the error messages regarding unconfigured packages)
Then I went for aptitude install libc6-dev and ignored the initial suggested option, I accepted the second option and initially it seemed to be trying to install the correct libc6-dev version.

Now it is complaining about libsysd-login0 contains empty filename though. This package was one of the packages that was autoremoved.
I think all my actions made a mess of the dependencies. Probably better to start from scratch and try again. I think I will use the image for Jessie then.

Thanks for your help marmistrz