* Removed some warnings
* Rebase with master
* Solved C++ Google Tests errors made by refactoring in order to remove warnings
* Undo renaming path -> path_
* Fix style check
Co-authored-by: Hyunsu Cho <chohyu01@cs.washington.edu>
* Now it's built as part of libxgboost.
* Set correct C API error in RABIT initialization and finalization.
* Remove redundant message.
* Guard the tracker print C API.