iss3102: make extension test submenu in TestCpp scrollable to access all entries
Merge branch 'iss3102-extensionstest-menuscroll' of https://github.com/hannon235/cocos2d-x into hannon235-iss3102-extensionstest-menuscroll
closed #2384: Using static_cast instead of C cast in ExtensionsTest.cpp.
Merge pull request #3105 from dumganhar/hannon235-iss3102-extensionstest-menuscroll

Merge PR https://github.com/cocos2d/cocos2d-x/pull/3103