Issue description

I get the warning about my compiler not being ABI-compatible even though it is.
I think the issue is due to CXX not being set, which defaults to c++ and the ABI-compatibility check is not properly done in https://github.com/pytorch/pytorch/blob/master/torch/utils/cpp_extension.py#L91, because c++ is not listed among the possible cases.

PyTorch version: 0.4.1
Is debug build: No
CUDA used to build PyTorch: 9.0.176

OS: Ubuntu 16.04.4 LTS
GCC version: (Ubuntu 5.4.0-6ubuntu1~16.04.10) 5.4.0 20160609
CMake version: version 3.5.1

Python version: 3.5
Is CUDA available: Yes
CUDA runtime version: 9.1.85
GPU models and configuration:
GPU 0: TITAN X (Pascal)
GPU 1: TITAN X (Pascal)
GPU 2: TITAN X (Pascal)
GPU 3: TITAN X (Pascal)

Nvidia driver version: 396.26
cuDNN version: Could not collect

Versions of relevant libraries:
[pip] Could not collect
[conda] Could not collect

Also my C++ version is 5.4.0