Re-add main menu credits button in M&P

For some reason, the credits button was always specifically removed from
M&P builds. After some discussion with Terry Cavanagh on the VVVVVV
Discord server, we agreed that there was no reason this should be
removed. So, it's getting put back in.

desktop_version/src/Game.cpp

@@ -6274,9 +6274,7 @@ void Game::createmenu( enum Menu::MenuName t, bool samemenu/*= false*/ )
         {
             option(loc::gettext("translator"));
         }
-#if !defined(MAKEANDPLAY)
         option(loc::gettext("credits"));
-#endif
         option(loc::gettext("quit"));
         menuyoff = -10;
         maxspacing = 15;

desktop_version/src/Input.cpp

@@ -399,9 +399,7 @@ static void menuactionpress(void)
         {
             OPTION_ID(3) /* translator */
         }
-#if !defined(MAKEANDPLAY)
         OPTION_ID(4) /* credits */
-#endif
         OPTION_ID(5) /* quit */
 
 #undef OPTION_ID
@@ -447,14 +445,12 @@ static void menuactionpress(void)
             game.createmenu(Menu::translator_main);
             map.nexttowercolour();
             break;
-#if !defined(MAKEANDPLAY)
         case 4:
             //Credits
             music.playef(Sound_VIRIDIAN);
             game.createmenu(Menu::credits);
             map.nexttowercolour();
             break;
-#endif
         case 5:
             music.playef(Sound_VIRIDIAN);
             game.createmenu(Menu::youwannaquit);