Implement utils::atof()
Change atof() to utils::atof()
Fix compile error
modify widget class comments
remove unused functions
Merge pull request #7440 from boyu0/add_utils_atof

Add utils::atof(), fix bug: particle not shown on android.
Merge pull request #7466 from andyque/fixPageView

remove unused functions
Merge pull request #7460 from andyque/fixComments

modify widget class comments
Merge branch 'v3' of https://github.com/cocos2d/cocos2d-x into v3_hot_fix