* save InferVarType changes, test=develop

* remove code comments, test=develop

* tweak code, test=develop

* fix compilation warning, update merge_ids_op split_ids_op to new interface, test=develop

* modify fused_bn_activation_op, test=develop

* fix error of fused_bn_activation_op, test=develop

* fix PADDLE_ENFORCE and unittest coverage issue, test=develop

* tweak PADDLE_ENFORCE messages, test=develop

* improve unittest coverage, test=develop

* add StaticGraphInferVarType class, test=develop

* rebase develop branch, test=develop

* fix unittest error, test=develop

* remove comments, test=develop

* improve unittest coverage, test=develop

* imporve error message and imporve unittest coverage, test=develop

* upgrade InferVarType API, test=develop

* tweak pyfunc error message, test=develop

* fix compilation conflict - save_combine_op, test=develop

* update index sample

* add kron op and its python API, doc and unittests.
* add kron in paddle.complex

* API/OP (affine_channel, group_norm, layer_norm, random_crop, unpool, log_loss) error message enhancement test=develop

* Add cholesky_op forward part. test=develop

* Complete cholesky_op forward part. test=develop

* Add cholesky_op backward part. test=develop

* Complete cholesky_op backward part. test=develop

* Refine cholesky_op error check and docs. test=develop

* Add grad_check unit test for cholesky_op. test=develop

* Fix sample code in cholesky doc. test=develop

* Refine some error messages of cholesky_op. test=develop

* Refine some error messages of cholesky_op. test=develop

* Remove unused input in cholesky_grad. test=develop

* Remove unused input in cholesky_grad. test=develop

* Fix stream for cusolverDnSetStream. test=develop

* Update PADDLE_ENFORCE_CUDA_SUCCESS from cholesky_op to adapt to latest code.
test=develop

* Add CUSOLVER ERROR in enforce.h
test=develop

* Fix the missing return value in cholesky. test=develop

* Add trainable_statistics in attr for batch_norm
* Unifying behavior of dynamic graph and static graph

test=develop

* change int to floor, test=develop

* fix unittest, test=develop

* test=develop

* support the head number == 1
test=develop

* fix slice op error.
test=develop

* Make batch_float_feasigns & batch_uint64_feasigns as member variable

* update name generator, test=develop

* use c++ unique name generator, test=develop

Fix the dygraph mode in matmul, add the support in Linear Op

* add the thread_local_allocator, test=develop

* refactor the thread_local_allocator, test=develop

* provides option setting strategy, test=develop

* add DataLoader, Dataset, BatchSampler

* add clamp api, test=develop

* OP(fusion_gru) error message enhancement. test=develop

* refine code, test=develop

* Refine inout log, test=develop

* Refine description, test=develop