fix many warnings (#889)

* fix many warnings

some of them can be solved by using a prototype-based system
maybe I can try to use some of these systems to reform backgrounds...

* Update app_mahjong.lua

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Co-authored-by: MrZ_26 <1046101471@qq.com>

parts/scenes/app_mahjong.lua

@@ -124,9 +124,9 @@ end
 function scene.mouseDown()
     _throwCard()
 end
-function scene.touchMove(x,y) scene.mouseMove(x,y) end
-function scene.touchDown(x,y) scene.mouseMove(x,y) end
-function scene.touchClick(x,y) scene.mouseDown(x,y) end
+scene.touchMove=scene.mouseMove
+scene.touchDown=scene.mouseMove
+scene.touchClick=scene.mouseDown
 function scene.keyDown(key)
     if key=='left' then
         if selected then