Change to the handling of -DCOMBINED in the makefiles. Instead of

defining it centrally per port, I think it's neater to define it for
each puzzle when adding that puzzle to the ALL list - because those
front ends which take -DCOMBINED are precisely those which use ALL.
In particular, this change opens up the possibility of compiling
both individual puzzles _and_ a combined monolith within the same
makefile.

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@8178 cda61777-01e9-0310-a592-d414129be87e