Port is_set_to from TH/THC to ATen.
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/28425
Test Plan: Imported from OSS
Differential Revision: D18063328
Pulled By: gchanan
fbshipit-source-id: 86af01a630d88c30947b8c85d1fac86dd7b40585
