* Transpose-Flatten-Concat fusion operator.
* Add unit testing and fix bug.

fix compile

fix Mac unittest error on reading pined memory flag

*  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

Merge branch 'fix_mac/fix_pinned_memory' of https://github.com/JiabinYang/Paddle into fix_mac/fix_pinned_memory

* 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