dmxgus: Add 'do not edit' message.
dmxgus: Add 'do not edit' message.

As the DMXGUS lump is autogenerated, add an explicit instruction not
to edit the lump, as someone might do so, naively seeking to improve
it.

jmtd/freedoom,CWolfRU/freedoom,jmtd/freedoom,CWolfRU/freedoom,jmtd/freedoom