Add proper notes about compatibility in README.txt

README.txt

@@ -8,7 +8,18 @@ in the Minetest Engine.
 The Minetest Engine can be found in:
   https://github.com/celeron55/minetest/
 
-This has been tested to work with the version tagged 0.4.dev-20120326.
+Compatibility
+--------------
+The minetest_game github master HEAD is generally compatible with the github
+master HEAD of minetest.
+
+Additionally, when the minetest engine is tagged to be a certain version (eg.
+0.4.dev-20120326), minetest_game is tagged with the version too.
+
+When stable releases are made, minetest_game is packaged and made available in
+  https://github.com/celeron55/minetest_game/downloads
+and in case the repository has grown too much, it may be reset. In that sense,
+this is not a "real" git repository. (Package maintainers please note!)
 
 License of source code
 ----------------------