Clarify references to Make and Play in README

Some people might be confused by the reference to M&P in the
instructions referring to downloading data.zip (TerryCavanagh#1026).

data.zip is the same between M&P and full versions of the game and is
orthogonal to which version of the game is built. Building M&P just
requires uncommenting `#define MAKEANDPLAY` in `MakeAndPlay.h`.

So clarify that you can grab data.zip from your existing copy of the
game, or from the Make and Play _page_ (not necessarily the Make and
Play edition of the game), and add instructions for building the M&P
version.

Closes TerryCavanagh#1027.

Author: InfoTeddy

desktop_version/README.md

@@ -23,6 +23,9 @@ Steamworks support is included and the DLL is loaded dynamically, you do not
 need the SDK headers and there is no special Steam or non-Steam version. The
 current implementation has been tested with Steamworks SDK v1.46.
 
+To build the Make and Play edition of the game, uncomment `#define MAKEANDPLAY`
+in `MakeAndPlay.h`.
+
 To generate the projects on Windows:
 ```
 # Put your SDL2 folders somewhere nice!
@@ -59,11 +62,10 @@ each time Xcode updates.
 
 Including data.zip
 ------------
-You'll need the data.zip file from VVVVVV to actually run the game! It's
-available to download separately for free in the
-[Make and Play](https://thelettervsixtim.es/makeandplay/)
-edition of the game. Put this file next to your executable and the game should
-run.
+You'll need the data.zip file from VVVVVV to actually run the game! You can grab
+it from your copy of the game, or you can download it for free from the [Make
+and Play](https://thelettervsixtim.es/makeandplay/) page. Put this file next to
+your executable and the game should run.
 
 This is intended for personal use only - our license doesn't allow you to
 actually distribute this data.zip file with your own forks without getting