* Add digamma_op and unittest

* add digamma_op api

* remove special DigammaCudaKernel and correct some docs

* remove unused headers

* fix api doc error

This reverts commit b2afc8df.

* add warning log for DataLoader output format imcompatible upgrade. test=develop

* Eliminate numerical differences of LayerNorm; fix LayerNorm Nan Bug while large data input

* fix bug while large shape of data input

* add support for trt dynamic shape flatten op

* add version restriction

* add ut input dynamic shape

* Small changes related to BF16 fusion_gru and fusion_lstm

* Correct to pass arg by value

* Add conditions to rnn op

* Correct the spelling mistake

* Improving the test with checking activation

* Trigger CI

* fix gather shape bug

* fix None

* fix topo

For python, if users write `a, b = var`, the `__getitem__` method will iterate through 0, 1, 2 ... until `__getitem__` throws an IndexError, then stop. The var[0], var[1] will be given to a, b respectively. If more values are given, the unpack size would cause error.

We didn't raise the IndexError in the past and we add statement in `__getitem__` to raise IndexError here to support grammar like `a, b = var` in this PR.

* fix Undefined variables

* fix Undefined variables

Change-Id: I4e09e7710f6693bff5388983270781a4ef70519e

* add check nan of inf for dygraph

* add unittest for dygraph

* revert error change

As the title

* support diff dataset tensor place in single process dataloader

* fix unittest failed

* fuse L2Decay and momentum when param.regularizer is set

* add unittest

* refine

* refine _create_regularization_of_grad of momentum

* improve append_optimizer_op

* add paddle.neg api

* add test for neg

* fix an English gammar error in comment

* add lgamma api

* support api paddle.tensor.neg() and paddle.tensor.lgamma()

* modify test_neg_op.py

* update, test=develop

* Support append customize attributes into op_desc in nn.Layer

* fix code style

* support override

* add unittest

* add random state generate in DataLoader worker. test=develop

* add parallel_cross_entropy

* add grad for crossentropy

* fix cross entropy

* support state_dict save to memory.

* Perfect unittest

* perfect unittest.

* suport saving binary var to memory

* polish code.

* packag save/load files into pybind/io.py

* polish code .

* add example for save to memory; remove useless save load function(_load_static_dict,_save_dygraph_dict)

* delete _load_static/dygraph_dict;_save_static/dygraph_dict

* edit example of paddle.save/load

* modify API nn.Bilinear's doc, test=develop

* add two attributes for yolo box

* Add wrap for functional api
* Refine the wraped api
* Add unit test for quant functional layers
* Update all unit tests for dygraph qat

* replace 'InnerSetOverridedStopGradient' with 'SetOverridedStopGradient'.

* improve coverage.

* polish error message.

* add dynamic layer_norm plugin

* fix bug

* fix numpy.allclose

* fix format

* fix code style

* remove shepe in dynamic shape

* code format

* remove layer norm fp16

* fix format