Fix contribution doc

better profiler and benchmark

fix two bugs

Add random crop op

Merge branch 'dev_add_random_crop_op' of https://github.com/JiayiFeng/Paddle into dev_add_random_crop_op

Merge branch 'dev_add_random_crop_op' of https://github.com/JiayiFeng/Paddle into dev_add_random_crop_op

add auto_grown_mutex for selected rows

Correct uint8 support

* Develop a fake dequantized op for fixed-point quantization training framework.

* Add the missing file.

Top K algorithm: parallel version

fix neon depthwise conv bug

* modify old machine translation

* modify new_api machine translation

* 1. implement StopAll in ListenAndServOp
2. make pserver receive the SIGINT and SIGTERM from outside
3. add unittests for listen_and_serv_op in python

* 1. add blocking queue set to record queue
2. aware all blocking queue when exit and exit gracefully

* 1. Remove comment lines from blocking_queue.h
2. Implement SignalHandler and move all global vars and funcs into it

* 1. Make code follows the style check
2. Move the SignalHandler out of the unnamed namespace

* 1. Make yapf happy

* 1. Call Stop() in destructor to release the resource allocated by ListendAndServOp
2. Change exit status to EXIT_SUCCESS after handling the signal from outside
3. Remove the mis-usage of REMOVE_ITEM in unittests

* 1. use DISABLE_COPY_AND_ASSIGN
2. use program once macro only

* update benchmark doc

* update by comment

Fix and optimize async distribute lookup table