[pyper] export caffe2 bucketize GPU operator to pytorch

Summary: Exporting the Bucketize operator on CUDA. Also adding unit test.

Test Plan: buck test mode/dev-nosan caffe2/torch/fb/sparsenn:gpu_test -- test_bucketize

Differential Revision: D23581321

fbshipit-source-id: 7f21862984c04d840410b8718db93006f526938a

Author: xw285cornell

caffe2/operators/bucketize_op.cu

@@ -52,3 +52,9 @@ bool BucketizeOp<CUDAContext>::RunOnDevice() {
 
 REGISTER_CUDA_OPERATOR(Bucketize, BucketizeOp<CUDAContext>);
 } // namespace caffe2
+
+using BucketizeCUDA = caffe2::BucketizeOp<caffe2::CUDAContext>;
+
+C10_EXPORT_CAFFE2_OP_TO_C10_CUDA(
+    Bucketize,
+    BucketizeCUDA);

caffe2/operators/bucketize_op.h

@@ -9,7 +9,7 @@
 #include "caffe2/core/operator.h"
 #include "caffe2/utils/math.h"
 
-C10_DECLARE_EXPORT_CAFFE2_OP_TO_C10(BucketizeOp);
+C10_DECLARE_EXPORT_CAFFE2_OP_TO_C10(Bucketize);
 
 namespace caffe2 {