Fix Flip Mode persisting in in-game options menu

Now graphics.flipmode is turned off when going into the menu, and turned
back on if necessary when exiting.

desktop_version/src/Input.cpp

@@ -2143,6 +2143,7 @@ void mapmenuactionpress()
         // Graphic options and game options
         music.playef(11);
         game.gamestate = TITLEMODE;
+        graphics.flipmode = false;
         game.ingame_titlemode = true;
         if (game.menupage == 32)
         {