Substantial infrastructure upheaval. I've separated the drawing API

as seen by the back ends from the one implemented by the front end,
and shoved a piece of middleware (drawing.c) in between to permit
interchange of multiple kinds of the latter. I've also added a
number of functions to the drawing API to permit printing as well as
on-screen drawing, and retired print.py in favour of integrated
printing done by means of that API.

The immediate visible change is that print.py is dead, and each
puzzle now does its own printing: where you would previously have
typed `print.py solo 2x3', you now type `solo --print 2x3' and it
should work in much the same way.

Advantages of the new mechanism available right now:
 - Map is now printable, because the new print function can make use
   of the output from the existing game ID decoder rather than me
   having to replicate all those fiddly algorithms in Python.
 - the new print functions can cope with non-initial game states,
   which means each puzzle supporting --print also supports
   --with-solutions.
 - there's also a --scale option permitting users to adjust the size
   of the printed puzzles.

Advantages which will be available at some point:
 - the new API should permit me to implement native printing
   mechanisms on Windows and OS X.

[originally from svn r6190]

Recipe

@@ -14,7 +14,7 @@
 !makefile osx Makefile.osx
 
 WINDOWS  = windows user32.lib gdi32.lib comctl32.lib comdlg32.lib
-COMMON   = midend misc malloc random version
+COMMON   = midend drawing misc malloc random version
 NET      = net tree234 dsf
 NETSLIDE = netslide tree234
 MINES    = mines tree234
@@ -28,26 +28,28 @@ ALL      = list NET NETSLIDE cube fifteen sixteen rect pattern solo twiddle
          + MINES samegame FLIP guess PEGS dominosa UNTANGLE blackbox SLANT
          + lightup MAP
 
-net      : [X] gtk COMMON NET
-netslide : [X] gtk COMMON NETSLIDE
-cube     : [X] gtk COMMON cube
-fifteen  : [X] gtk COMMON fifteen
-sixteen  : [X] gtk COMMON sixteen
-rect     : [X] gtk COMMON rect
-pattern  : [X] gtk COMMON pattern
-solo     : [X] gtk COMMON solo
-twiddle  : [X] gtk COMMON twiddle
-mines    : [X] gtk COMMON MINES
-samegame : [X] gtk COMMON samegame
-flip     : [X] gtk COMMON FLIP
-guess    : [X] gtk COMMON guess
-pegs     : [X] gtk COMMON PEGS
-dominosa : [X] gtk COMMON dominosa
-untangle : [X] gtk COMMON UNTANGLE
-blackbox : [X] gtk COMMON blackbox
-slant    : [X] gtk COMMON SLANT
-lightup  : [X] gtk COMMON lightup
-map      : [X] gtk COMMON MAP
+GTK      = gtk printing ps
+
+net      : [X] GTK COMMON NET
+netslide : [X] GTK COMMON NETSLIDE
+cube     : [X] GTK COMMON cube
+fifteen  : [X] GTK COMMON fifteen
+sixteen  : [X] GTK COMMON sixteen
+rect     : [X] GTK COMMON rect
+pattern  : [X] GTK COMMON pattern
+solo     : [X] GTK COMMON solo
+twiddle  : [X] GTK COMMON twiddle
+mines    : [X] GTK COMMON MINES
+samegame : [X] GTK COMMON samegame
+flip     : [X] GTK COMMON FLIP
+guess    : [X] GTK COMMON guess
+pegs     : [X] GTK COMMON PEGS
+dominosa : [X] GTK COMMON dominosa
+untangle : [X] GTK COMMON UNTANGLE
+blackbox : [X] GTK COMMON blackbox
+slant    : [X] GTK COMMON SLANT
+lightup  : [X] GTK COMMON lightup
+map      : [X] GTK COMMON MAP
 
 # Auxiliary command-line programs.
 solosolver :    [U] solo[STANDALONE_SOLVER] malloc
@@ -123,7 +125,7 @@ Puzzles.dmg: Puzzles
 # it in the Makefile because it will be worse than useless if it
 # ever fails to compile, so it's important that it should actually
 # be built on a regular basis.
-nullgame : [X] gtk COMMON nullgame
+nullgame : [X] GTK COMMON nullgame
 nullgame : [G] WINDOWS COMMON nullgame
 
 # Version management.