Merge pull request #6725 from dumganhar/ref-tracker

Adds ref memory tracker to easily find out memory leak for instance of Ref or its subclasses
fix the compile error in Xcode 4.6 for mac platform which trigger by the Architectures’ value
Merge branch 'v3' of https://github.com/cocos2d/cocos2d-x into v3_fix
[ci skip], set v2-branch different variable in pull-request-builder.py.
Merge pull request #6733 from shujunqiao/pull-build-branch

[ci skip], set v2-branch different variable in pull-request-builder.py.
Merge pull request #6732 from samuele3hu/v3_fix

fix compile error in Xcode 4.6 for mac platform which trigger by the Architectures’ value