New mechanism for automatic generation of the puzzle screenshots on

the web, which I hope will also end up being extended to generate
both Windows and X icons for each individual puzzle. The mechanism
is: for each puzzle there's a save file in the `icons' subdirectory
showing a game state which I think is a decent illustration of the
puzzle, and then there's a nasty set of scripts which runs each
puzzle binary, loads that save file, grabs a screenshot using xwd,
and munges it into shape.

In order to support this I've added two new options (--redo and
--windowid) to all the GTK puzzles, which I don't expect ever to be
used outside the icons makefile. I've also added two more options
(--load and --id) which force a GTK puzzle to treat its command-line
option as a save file or as a game ID respectively (the previous
behaviour was always to guess, and sometimes it guessed wrong).

[originally from svn r7014]

icons/samegame.sav

@@ -0,0 +1,34 @@
+SAVEFILE:41:Simon Tatham's Portable Puzzle Collection
+VERSION :1:1
+GAME    :9:Same Game
+PARAMS  :9:10x10c3s2
+CPARAMS :9:10x10c3s2
+SEED    :15:785412408200083
+DESC    :199:1,1,3,1,2,2,1,2,3,2,2,2,3,3,2,1,1,1,3,2,3,3,2,3,1,3,2,1,1,3,1,2,2,2,3,2,3,2,3,2,1,3,1,2,1,2,3,2,1,3,2,3,1,1,3,3,1,3,3,3,1,1,3,2,2,1,1,2,1,2,2,2,3,1,3,2,2,1,2,3,3,1,2,3,1,3,3,2,1,3,3,1,3,1,2,2,1,3,1,2
+NSTATES :2:26
+STATEPOS:2:13
+MOVE    :6:M94,95
+MOVE    :6:M83,84
+MOVE    :9:M83,93,94
+MOVE    :6:M93,94
+MOVE    :6:M20,21
+MOVE    :15:M20,21,22,31,32
+MOVE    :6:M70,71
+MOVE    :6:M80,90
+MOVE    :9:M73,82,83
+MOVE    :18:M72,73,74,82,83,92
+MOVE    :12:M51,61,62,72
+MOVE    :9:M35,36,46
+MOVE    :12:M49,57,58,59
+MOVE    :6:M59,69
+MOVE    :9:M69,79,89
+MOVE    :12:M78,79,89,99
+MOVE    :24:M45,46,47,54,55,57,64,67
+MOVE    :36:M36,46,55,56,57,66,67,68,77,78,88,98
+MOVE    :9:M76,77,87
+MOVE    :6:M97,98
+MOVE    :6:M94,95
+MOVE    :45:M50,60,61,70,71,81,82,83,84,85,90,91,92,93,94
+MOVE    :12:M73,81,82,83
+MOVE    :6:M92,93
+MOVE    :9:M81,90,91