Fix warnings generated by gcc 4.6.0 about variables set but not

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