* move reduce_all_flag from python to c++

* fix infer shape bug

* fix bug;

* fix sum infer meta bug

* fix reduce sum grad gpu bug

* fix amin amax bug;

* add paddle.nn.functional.pairwise_distance (cattidea/Paddle#273)
* remove the test case for undefined behavior
Co-authored-by: NSigureMo <sigure.qaq@gmail.com>