Stop the Pattern grid generation from generating an entire row or
column of the same colour (at least when the dimensions are big
enough to make this feasible). It's a little bit too easy otherwise!

[originally from svn r5391]
Oops. Just noticed that the Windows front end completely ignores the
`colour' parameter in draw_text().

[originally from svn r5507]
Initial checkin of `Solo', the number-placing puzzle popularised by
the Times under the name `Sudoku'.

[originally from svn r5660]
Visual C points out a couple of typos.

[originally from svn r5661]
Simplify clip region handling under Windows, which also makes Solo's
clipping policy work properly. I haven't proved why it didn't work
the previous way, but I have a good guess: I think that clip regions
are handled by reference. So I saved the old clip region out of the
DC, then did an IntersectClipRect, and then selected the old clip
region back in again - but the old clip region had never been
_de_-selected, because IntersectClipRect didn't change which object
was selected but rather it modified-in-place the one that already
was selected. So my attempt to restore the old clip region did
nothing whatsoever, and thus clipping to two different rectangles
during the same draw sequence failed. Now I'm completely destroying
the clip region during unclip(), which seems to work better.

[originally from svn r5662]
Doc tweaks for Solo.

[originally from svn r5665]
Introduce configurable symmetry type in generated puzzles, and drop
the default symmetry from order-4 down to order-2, which seems to
mitigate the excessively-full-grid problem by permitting more
freedom to remove stuff.

[originally from svn r5666]
Outstandingly cute mathematical transformation which allows me to
lose a lot of code duplication in nsolve while preserving efficiency.

[originally from svn r5667]
Various changes prompted by my boss taking an interest:
 - added a compilation option -DSTANDALONE_SOLVER which makes both
   of Solo's internal solvers accessible from the command line.
 - fix a bug in nsolve turned up by testing in this mode: it failed
   to iterate at all! Oddly, this massive improvement to the
   effectiveness of nsolve hasn't emptied the generated grids by
   very much.
 - add an extra mode of reasoning to my to-do list (which is the
   dual of one already there, so I'm kicking myself).

[originally from svn r5670]
Oops; _actually_ add the reasoning mode I mentioned in the last
checkin.

[originally from svn r5671]
Remove some legacy debugging code which was breaking the MinGW
build, and which is redundant given the new standalone solver
functionality.

[originally from svn r5672]
Fix trivial UI glitch involving clicking on the border outside the
grid. I'm really starting to get annoyed by the default round-
towards-zero behaviour of C integer division.

[originally from svn r5681]
Implement the remaining modes of reasoning in nsolve, and thus
enable configurable puzzle difficulty. I'm only generating grids up
to Times level (complicated non-recursive analysis but guessing
never required); I wouldn't object to providing a Telegraph
difficulty level (guessing required) but it turns out to be very
hard indeed to generate at random. I might still add it later
(probably under the name `Unreasonable' :-) if I can think of an
efficient way to find them.

[originally from svn r5682]
The command-line solver's difficulty gradings now use the same
terminology as the puzzle GUI.

[originally from svn r5683]
Pattern also contains an internal solver, so here's a command-line
interface to it just in case it comes in handy.

[originally from svn r5686]
Command-line solver was dividing up non-square puzzles the wrong way
round.

[originally from svn r5691]
Patches for GTK 2. Puzzles already _built_ under GTK 2, but now it
builds better:
 - the GTK makefile now defines $(GTK_CONFIG) which you can
   override, so you can build for GTK 2 with no makefile-editing
   simply by running `make GTK_CONFIG="pkg_config gtk+-2.0"'
 - we use Pango to find appropriate fonts, which means the text in
   the puzzles actually (gasp!) adapts its size to the
   circumstances. Unfortunately, I've been unable to do this
   portably without depending on _either_ a Pango function that
   isn't present in older versions _or_ the underlying window system
   being X11; I'd appreciate someone doing better.

[originally from svn r5693]
Fix inconsistent vertical centring of text in GTK (and update Solo's
todo list, which complained about this because Solo was the only
puzzle noticeably affected).

[originally from svn r5694]
Aha, even better: a Makefile hack that causes auto-detection of GTK
2 and fallback to GTK 1.2.

[originally from svn r5705]
Correct block coordinate display when standalone solver shows its
working.

[originally from svn r5706]