Fix warnings generated by gcc 4.6.0 about variables set but not

thereafter read. Most of these changes are just removal of pointless
stuff or trivial reorganisations; one change is actually substantive,
and fixes a bug in Keen's clue selection (the variable 'bad' was
unreferenced not because I shouldn't have set it, but because I
_should_ have referenced it!).

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@9164 cda61777-01e9-0310-a592-d414129be87e