* type promotion for grad

* add type promotion for div op

* test=develop,test=document_fix, remove the out args

* Revert "test=develop,test=document_fix, remove the out args"

This reverts commit f430799b.

* test=develop,test=document_fix, remove the out args

* remove all  the out args

* remove all  the out args

* test=develop, remove all  the out args

* test=develop, remove all  the out args

* test=develop, remove out args in matmul testcase

* test=develop, fix the bugs of out args testcase in logsumexp

* test=develop, fix the bugs of out args testcase in elementwise_add

* test=develop, fix the bugs of out args testcase in elementwise_div

* test=develop, fix the bugs of out args testcase in activation

* test=develop, fix the bugs of out args testcase in addcmul

* test=develop, fix the bugs of out args

* test=develop, fix the bugs of out args in API example

* test=develop, fix the bugs of out args in kron testcase

* test=develop, fix the bugs of out args in kron testcase

* test=develop, remove out args

* test=develop, remove out args

* test=develop, fix the coverage

* test=develop, polish codestyle

* test=develop, Update math.py

* test=develop, polish codestyle

* test=develop, polish codestyle

* test=develop, polish codestyle

* test=develop, polish codestyle

* test=develop, polish the test_activation_op.py

* test=develop, Update math.py

* test=develop, fix the failed CI

* test=develop, add core.ops

* test=develop, add core.ops change clamp to clip

* test=develop, add core.ops change clamp to clip

* test=develop, write testcase for clamp OP

fix kron_op: when only one input needs gradient

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