Merge pull request #2075 from dingpinglv/Iss5781_ReleaseV3rc2

Fixed #5781: update the build.xml for v3.0 rc2
Fixed #5977: Add cc.sys.platform and improve inline document
Merge branch 'develop' of git://github.com/cocos2d/cocos2d-html5 into develop
Merge pull request #2076 from pandamicro/develop

Fixed #5977: Add cc.sys.platform and improve inline document
Fixed #5781: fixed a bug of cc.Sprite that its setVisible is invalid when using BatchNode
Merge branch 'develop' of git://github.com/cocos2d/cocos2d-html5 into Iss5781_ReleaseV3rc2