Initialize level data with 0s in M&P

Following discussion on TerryCavanagh/VVVVVV#153, I suggested that
instead of reverting my M&P guards from TerryCavanagh/VVVVVV#124 (which
would only revert it for The Final Level, The Lab, Overworld, and The
Tower, leaving Space Station 1 & 2 and The Warp Zone alone which could
potentially cause the same problem that motivated
TerryCavanagh/VVVVVV#153), we should initialize the map data with 0s
instead.

desktop_version/src/MakeAndPlay.h

@@ -5,6 +5,6 @@
  * It's heaps faster than rebuilding everything, so here we are.
  * -flibit
  */
-// #define MAKEANDPLAY
+#define MAKEANDPLAY
 
 #endif /* MAKEANDPLAY_H */