Solve the crash in WebSocketTest when the network in disconnected.
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into develop
closed #4150:  fix physics position/rotation tag bug.
Merge pull request #5589 from natural-law/develop

Solve the crash in WebSocketTest when the network in disconnected.
check validation of ndk_root
Merge pull request #5594 from minggo/install

check validation of ndk_root
Merge pull request #5593 from boyu0/iss4159_physics_position_rotation_bug

closed #4159:  fix physics position/rotation tag bug.
Merge branch 'develop' into develop_nutty_modify_framework_for315