This is an extension for AndEngine which adds supports for Box2D physics. All physics-related examples from AndEngineExamples repository depend on it.
This extension depends on the code libgdx library, so to make the project
build, you have to run UPDATE_LIBGDX_SOURCES.sh or UPDATE_LIBGDX_SOURCES.cmd
(depending on your platform). These batch scripts will sync the latest code from
libgdx repo.