Fix and update eduke32
Since https://git.savannah.gnu.org/cgit/guix.git/commit/?id=2073b55 eduke32 fails to build because it overrides CPLUS_INCLUDE_PATH. Setting SDL include path doesn’t appear to be necessary (anymore), so we can avoid the issue by not doing it.
The second patch updates eduke32 to latest master, which supports Ion Fury 1.1.