getter always must be a const method.
Merge branch 'FixNodeConst' of https://github.com/zifter/cocos2d-x into FixNodeConst

Conflicts:
	cocos/ui/UIListView.h
	cocos/ui/UIPageView.h
Merge pull request #6721 from zifter/FixNodeConst

[ci skip]Getter always must be a const method.