Add a README.

[originally from svn r4194]

README

@@ -0,0 +1,29 @@
+This is the README accompanying the source code to Simon Tatham's
+puzzle collection.
+
+You should find several Makefiles in the source code:
+
+ - `Makefile.gtk' should work under GNU make on Linux, provided you
+   have GTK installed to compile and link against. It builds GTK
+   binaries of the puzzle games.
+
+ - `Makefile.vc' should work under MS Visual C++ on Windows.
+
+ - `Makefile.cyg' should work under Cygwin / MinGW. With appropriate
+   tweaks and setting of TOOLPATH, it should work for both compiling
+   on Windows and cross-compiling on Unix.
+
+Each of these Makefiles builds a program called `nullgame' in
+addition to the actual game binaries. This program doesn't do
+anything; it's just a template for people to start from when adding
+a new game to the collection, and it's compiled every time to ensure
+that it _does_ compile and link successfully (because otherwise it
+wouldn't be much use as a template). Once it's built, you can run it
+if you really want to (but it's very boring), and then you should
+ignore it.
+
+DO NOT EDIT THE MAKEFILES DIRECTLY, if you plan to send any changes
+back to the maintainer. The makefiles are generated automatically by
+the Perl script `mkfiles.pl' from the file `Recipe'. If you need to
+change the makefiles as part of a patch, you should change Recipe
+and/or mkfiles.pl.