1. v2.layer.parse_network does not correctly handle the generation output.
2. GatherAgentLayer does not correctly handle generation output when batch_size > 1
3. Fix CustomStackTrace for rnn group

No longer need to use SubsequenceInput. The framework will detect.

* When SWIG_PY is not enabled, paddle.v2 package cannot be used.
* When PYTHON is not enabled, PyDataProvider cannot be used.

Fix issue #1920

* When SWIG_PY is not enabled, paddle.v2 package cannot be used.
* When PYTHON is not enabled, PyDataProvider cannot be used.

Fix issue #1920

* Check all files by pre commit hooks

* add interface and unittest for nce layer

* follow comments

* Use C++ 11 atomic_flag in MacOS as spin lock
* Add unittest for it.

* follow comments to fix bugs

* refine sparse momentum api and unittest
* fix unittests bug

* reduce trainer count for unit test on MAC OSX

* Add `device` parameter to ExtraAttr in trainer_config_helpers.
* add unittest for it.

* remove unnecessary field set in ParameterConfig, Evaluators, etc

ISSUE=4586495

git-svn-id: https://svn.baidu.com/idl/trunk/paddle@1408 1ad973e4-5ce8-4261-8a94-b56d1f490c56