OpenGL context attributions setting
merge v3 to v3_glviewattrs
OpenGL context attributions setting revise
Merge branch 'v3' of https://github.com/cocos2d/cocos2d-x into v3_glviewattrs
OpenGL context attributions setting revise -2
Merge pull request #7843 from huangshiwu/v3_glviewattrs

V3 glviewattrs