Merge pull request #1039 from linshun/iss2580_v2.1.5

issue #2580: merged v2.1.5 to master branch
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 #1054 from dingpinglv/Iss_FixBuildxmlBug

Fixed a bug that engine can't load from single engine file