Code to construct Windows icon files for the puzzles, by munging the

Code to construct Windows icon files for the puzzles, by munging the
screenshots into appropriate sizes and colour depths. This is all
done with a nasty Perl script, because ImageMagick does not output
correct .ICO format. Not sure why; it isn't _that_ hard.

I intend at some point to link the resulting icons into the actual
Windows puzzle binaries, but before then I have to make them
prettier: most of them would benefit from being derived from a
smaller crop of the puzzle screenshot instead of trying to fit the
whole thing in.

[originally from svn r7017]