After discussion with Simon, the game redraw functions are now passed a new

After discussion with Simon, the game redraw functions are now passed a new
argument `dir' which tells them whether this redraw is due to an undo, rather
than have them second-guess it from game state.
Note that none of the actual games yet take advantage of this; so it hasn't
been tested in anger (although it has been inspected by debugging).

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@4469 cda61777-01e9-0310-a592-d414129be87e