closed #4424: fix PhysicsBody::setGravity() doesn't work correctly sometimes.
closed #4424: change name _enable->_enabled, _rotationEnable->_rotationEnabled, _gravityEnable->_gravityEnabled
closed #4419,  Backup the environment  file when adding environment variable in setup.py.
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into develop
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into develop
Merge pull request #5854 from boyu0/iss4424_setgravityenable_fix

closed #4424: fix PhysicsBody::setGravityEnable() doesn't work correctly sometimes
Update CHANGELOG [ci skip]
Merge pull request #5882 from natural-law/develop

Backup the environment  file when adding environment variable in setup.py.