Record locations of pooling region.

[MonPower]

Could we remember the locations of pooling operation such max pooling. So that we could reverse the pooling operation approximately.

[xiuliren]

@MonPower as I remember, torch has offset inference, could be useful for your case. I have not tried yet though.

[szha]

This code base has been donated to the Apache MXNet project per #373, and repo is deprecated. Future development and issue tracking should continue in Apache MXNet.