Allow game backends to use even special keystrokes such as N and Q;

Allow game backends to use even special keystrokes such as N and Q;
they will only be processed as special by the midend if unwanted by
the backend. This causes 5x5 Solo to become just about playable,
because you can now click in a square and type `n'. However, typing
`n' when a square is not selected will revert to the normal
behaviour of starting a new game.

(This isn't particularly ideal, I know, but it's better than
nothing.)

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@6048 cda61777-01e9-0310-a592-d414129be87e