I have now reloaded the package information in Synaptic and upgraded the proposed packages. In Synaptic I see libxwbase 2.8.11.0-0 and the other files needed for CodeBlocks marked with the green square but all of them have 0 Byte in the column Download. This seems to be normal though, because other program packages, e.g. Wine, that I have downloaded from other places than the Mepis repository also have 0 Bytes in Synaptic. So the problem now, I believe, is not that the computer misses files like new enough versions of libxwbase, but that the installation of the CodeBlocks DEB packages breaks one another when trying to install them with the help of Synaptic. Maybe I should install an RPM-based distribution alongside Mepis Linux and try installing CodeBlocks with an RPM package. What do you think?