* optimization check_api_approvals

* change echo line

* echo_line

* update

* test=develop;test=document_fix

* change api document review;test=develop;test=document_fix

* test=develop;test=document_fix

* make Docker to gcc 8.2, test=develop

* add -std=c11 to grpc.cmake, test=develop

* fix PADDLE_ENFORCE ci check bug, test=develop, test=document_fix

* fix PADDLE_ENFORCE match error, test=develop, test=document_fix

* add ci check for error message specification, test=develop, test=document_fix

* replace spec url & refine failed message, test=develop, test=document_fix

* split api_spec document;test=document_fix

* change tools

* test=develop;test=document_fix

* test=develop;test=document_fix

* test=develop

* add op indicate var type method call check

* add error test example, test=develop, test=document_fix

* add count judge, test=develop, test=document_fix

* polish example detail, test=develop, test=document_fix

* test indicate var data type method, test=develop, test=document_fix

* test no get expect kernel type, test=develop, test=document_fix

* remove test case, test=develop test=document_fix

* mv sampcd_processor.py to tools

test=develop test=document_fix

* update example script

test=develop test=document_fix

* add support to gcc8, add docker env test=develop

* refine API.spec, test=develop

* add nn.py to test,test=develop

* fix by removing new.spec, test=develop, test=document_fix

* refine scripts when PYTHON_ABI is empty, follow partial comments, add extra cpp api doc, test=develop, test=document_fix

* remove extra doc changes, remove API.spec, test=develop

* refine print_signatures.py to remove ComposeNotAligned, test=develop

* remove experimental_namespace, test=develop

* correct then sample command of diff_api.py to align with paddle_build.sh

test=develop

* fix the api.spec file does not get the class comment problem

* cat new.spec

* check api.spec

* test=develop

* test=develop

* test=develop

add Dygraph api to api.spec

This change doesn't effect CI task because CI docker config build
was done in another way.

test=develop

The detail of 2 bugs:

tools/manylinux1/Dockerfile cannot build Cuda9 Cuda10 image on
CI. Fixed it and tested manually. Will test on CI after this PR is
merged.

tools/manylinux1/build_scripts/install_nccl2.sh doesn't have
Cuda10 version. Added it

test=develop

* test=develop

* test=develop

* test=develop

* del #

* test=develop

* test=develop

* document_preview

* change name

* document

* add document_preview.sh

* add document_preview.sh

* add paddle_build.sh

* nohup python

* change port runserver

* test doc

* test=develop

* test=develop

* test=develop

* add git clone FluidDoc,PaddlePaddle.org

* change PaddlePaddle.org

* Add port comment

* change directory

* change PADDLE_ROOT

test=develop

test=develop

2. Add binutils 2.27 in manylinux support

test=develop

* make timeline.py compatible
test=develop

* Follow comment
test=develop

test=develop