Merge pull request #1043 from linshun/iss2580_v2.1.5

Merged v2.1.5 to master branch
fixed a bug that engine can't load from single engine file
Merge pull request #1055 from dingpinglv/Iss_FixBuildxmlBug

fixed a bug that engine can't load from single engine file
Merge branch 'master' of github.com:cocos2d/cocos2d-html5