Clean up cast from c10::complex<T> to thrust::complex<T>, and update the workaround CUDA version to <10.2 (#38941)
Summary:
I'm using CUDA 10.1 on Debian buster but I can still experience
compilation issues:
```
/usr/include/thrust/detail/complex/complex.inl(64): error: no suitable conversion function from "const c10::complex<float>" to "float" exists
detected during:
instantiation of "thrust::complex<T>::complex(const R &) [with T=float, R=c10::complex<float>]"
/home/hong/xusrc/pytorch/c10/util/complex_type.h(503): here
instantiation of "T std::abs(const c10::complex<T> &) [with T=float]"
/home/hong/xusrc/pytorch/aten/src/ATen/native/cuda/AbsKernel.cu(17): here
instantiation of "c10::complex<T> at::native::abs_wrapper(c10::complex<T>) [with T=float]"
/home/hong/xusrc/pytorch/aten/src/ATen/native/cuda/AbsKernel.cu(29): here
/usr/include/thrust/detail/complex/complex.inl(64): error: no suitable conversion function from "const c10::complex<double>" to "double" exists
detected during:
instantiation of "thrust::complex<T>::complex(const R &) [with T=double, R=c10::complex<double>]"
/home/hong/xusrc/pytorch/c10/util/complex_type.h(503): here
instantiation of "T std::abs(const c10::complex<T> &) [with T=double]"
/home/hong/xusrc/pytorch/aten/src/ATen/native/cuda/AbsKernel.cu(17): here
instantiation of "c10::complex<T> at::native::abs_wrapper(c10::complex<T>) [with T=double]"
/home/hong/xusrc/pytorch/aten/src/ATen/native/cuda/AbsKernel.cu(29): here
2 errors detected in the compilation of "/tmp/hong/tmpxft_00005893_00000000-6_AbsKernel.cpp1.ii".
CMake Error at torch_cuda_generated_AbsKernel.cu.o.Debug.cmake:281 (message):
Error generating file
/home/hong/xusrc/pytorch/build/caffe2/CMakeFiles/torch_cuda.dir/__/aten/src/ATen/native/cuda/./torch_cuda_generated_AbsKernel.cu.o
```
`nvcc --version`:
```
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2019 NVIDIA Corporation
Built on Wed_Apr_24_19:10:27_PDT_2019
Cuda compilation tools, release 10.1, V10.1.168
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38941
Differential Revision: D21818790
Pulled By: ezyang
fbshipit-source-id: a4bfcd8ae701f7c214bea0731c13a5f3587b7a98
