Fixed #5549: [JSB] support ScrollView for clipping its content
Fixed #5561: fix addChild issues in Widget's addChild function
Fixed #5561: [2.x]Fix addChild issues in Layout and ScrollView's addChild function
Fixed #5561: [2.x]Fix addChild issue in Widget's addChild function
Merge pull request #7051 from pandamicro/v2

Bug Fixes