Make love.mouse.isDown accept a list too

Credits go to Boolsheet for making this patch (imported unmodified!)

src/modules/mouse/sdl/Mouse.h

@@ -43,7 +43,7 @@ namespace sdl
 		void getPosition(int & x, int & y) const;
 		void setPosition(int x, int y);
 		void setVisible(bool visible);
-		bool isDown(Button button) const;
+		bool isDown(Button * buttonlist) const;
 		bool isVisible() const;
 		void setGrab(bool grab);
 		bool isGrabbed() const;
@@ -59,4 +59,4 @@ namespace sdl
 } // mouse
 } // love
 
-#endif // LOVE_MOUSE_SDL_MOUSE_H
+#endif // LOVE_MOUSE_SDL_MOUSE_H