Customized pin_memory for PackedSequence (#18079)
Summary:
fixes https://github.com/pytorch/pytorch/issues/18078
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18079
Reviewed By: ezyang
Differential Revision: D14521192
Pulled By: zou3519
fbshipit-source-id: cec773a3a6f2c405a0d9701e213b7caf81649181
