Make lstm_op follow google code style.

add WITH_DOC for print_operators_doc

* Add DataFeeder

A v2 API like data feeder for book demos.
We can feed data directly from reader.

* Fix CI

* Remove batch_size_dim for feeder

Also add __all__ to data_feeder.py

* Follow comment

simplify the CMakeLists.txt of trainer/tests and gserver/tests

Fix the doc of LSTM operator.

* Add hinge loss op

* Update hinge-loss equation for proper latex

Simple pipe reader for hdfs or other service

Merge branch 'print_operators_doc' of https://github.com/luotao1/Paddle into luotao1-print_operators_doc

polish mkldnn doc

Fix the compiling error when seting WITH_C_API=ON and WITH_PYTHON=ON.

Add switch for distributed support

* fix grpc compile warn

* update

* -Wnon-virtual-dtor -> -Wno-non-virtual-dtor

* change GPU memory allocating policy

* fix potential overflow bug

* Expose sigmoid_cross_entropy_with_logits

Also, change the `labels` to `label` for api consistency

* Very simple GAN based on pure FC layers

Add version and commit information in capi config.h and use unofficial glog for Android API < 21. (#6113)

* Automatically configure the version and commit information in capi.

* Use the unofficial glog repository for building for Android (API < 21).

Add nce op

Also, change the `labels` to `label` for api consistency

Fix comments in sequence_rnn_(mixed/matched)_inputs.py

enable inference benchmark