Rename tempTexture to menuoffTexture

I'm going to soon be creating an actually temporary texture, so having
two textures named "temp" would get confusing. This is also a good
chance to correct the name of this texture, because it's not really
temporary, but it's used for map menu animation rendering.

desktop_version/src/Graphics.h

@@ -308,7 +308,7 @@ public:
     bool notextoutline;
 
     SDL_Texture* gameTexture;
-    SDL_Texture* tempTexture;
+    SDL_Texture* menuoffTexture;
     SDL_Texture* gameplayTexture;
     SDL_Texture* menuTexture;
     SDL_Texture* ghostTexture;