dehacked: Add magic comment for Chocolate Doom.

Chocolate Doom now has BEX [STRINGS] section support, but it must
be enabled using a magic comment inside the file. Add this comment
to the Freedoom DEHACKED lumps.
Merge branch 'master' of github.com:freedoom/freedoom
dehacked: Add copyright notice to lumps.

Include the Freedoom copyright notice in the DEHACKED lumps used
for Freedoom and FreeDM.