CPU-Strided-Complex Fixes for real and imag ops (#29840)
Summary:
In-tree changes to pytorch to support complex numbers are being submitted here.
Out-of-tree support for complex numbers is here: [pytorch-cpu-strided-complex extension](https://gitlab.com/pytorch-complex/pytorch-cpu-strided-complex)
- [x] Replaced std:real(a) with a.real() in kernel level code.
- [x] Fixed Vec256_base implementation of complex ops so that it works correctly on Non-AVX devices.
- [x] Fix NumericUtils.h
cc: iotamudelta, ezyang, bddppq, zasdfgbnm
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29840
Differential Revision: D18531274
Pulled By: ezyang
fbshipit-source-id: 0fa842c68e4bd55134fe0271880e2d15fe692b7f
