C++ SDK (upstream)

[headupinclouds]

Try to remove or merge non-standard features upstream. Initial list:

• cereal needed? > check current xgboost (de)serialization portability: 32/64-bit, big/little-endian?
• serialization redution? > measure current xgboost model size
• XGBOOST_DO_LEAN needed? > measure SDK for prediction only w/ -fdata-sections -ffunction-sections -lto

[headupinclouds]

xgboost v0.6.0 dependencies

xgboost (CMake=YES)
|-dmlc-core (CMake=YES)
|  [H] find_package(HDFS REQUIRED)
|  [Y] find_package(JNI REQUIRED)
|  [H]  find_package(CURL REQUIRED)
|  [H] find_package(OpenSSL REQUIRED)
|  [ ] find_package(Crypto REQUIRED)
|  [Y] find_package(OpenMP REQUIRED)
|  [ ]  find_package(PythonInterp)
|-rabit (CMake=NO)
|-cub (CMake=NO)
|-nccl (CMake=YES)
|    find_package(CUDA 7.5 QUIET REQUIRED)