fixed self assignment error and provide move semantics to pushBack of Vector<T>
remove const modifier of move semantic
Merge branch 'develop' of github.com:andyque/cocos2d-x into develop
Merge remote-tracking branch 'upstream/develop' into develop
fix move assignment operator doesn't clear previous content bug
remove unused code
Merge pull request #4815 from andyque/fix

ix move assignment operator doesn't clear previous content bug