*  fix mkdir conflict

*  fix load/save lookup tables

 test=develop

* add lookup_table_utils

* fix load optimize vars on pserver

* delete lookup table utils

* fix save and load lookup tables

* fix load optimizer var

* fix load optimizer var, test=develop

* fix python 3 style, test=develop

* move lookup_table_utils to contrib utils

refine prelu api doc

* Remove the memory copy for feeding data in C++ inference API
* Fix compling dependence
* Fix compling in ONLY_CPU mode

Fix increment_op doc

test=develop

* test=develop

remove code.

* test=develop

Fix cublas warp error

test=develop

Add python3.6 python3.7 support in ubuntu dockerfile

test=develop

Fix multiclass_nms_op unit test fail in python3.6

test=develop

test=develop

Merge branch 'develop' of https://github.com/PaddlePaddle/Paddle into add_py36_py37_ubuntu_dockerfile

add thread related inference api

test=develop

test=develop

Merge branch 'develop' of https://github.com/PaddlePaddle/Paddle into add_py36_py37_ubuntu_dockerfile

test=develop

test=develop

Refine split TensorRT plugin

test=develop

Add python 3.6 and python 3.7 support to paddle build

test=develop

test=develop

Fix pool2d doc and add pool2d test in test_layers

* HIP cmake.
Enable whole archieve build for pybind library.

Disable two warning.

Rollback to C++11.

Link RCCL to WA gpu kernel loading issue.

Update eigen to fix build failure.

Add more include directories.

Fix O3 build failure.

Update eigen.

fix tensor_util_test segment fault issue

add more macro check in hip.cmake.
we may consider refine hip.cmake to inherit all add_definitions() in parrent scope, in the future.

Fix rocRAND load.

Update eigen to fix gru_unit_op and reduce_op.

Add HIP support to testing.

Update eigen to support int16 and int8 in arg min and arg max.

* add rocprim as cub library used by nv implementation

* Reduce build time in rocprim.

* Add rocprim introduction, remove useless cmake code.

* Remove useless flags and format cmake file.

Add sqlite3 support in Python3.6

* CUDA kernel for density_prior_box_op.
* Support flatten to 2D.

Bumped MKL-DNN version to 0.17

Update issue templates

Add dlpack support