isnan, isfinite, and isinf are implemented as macros for MSVC

[bashbaug]

The CTS tests currently define isnan, isfinite, and isinf macros for MSVC: https://github.com/KhronosGroup/OpenCL-CTS/blob/40aaa2bcf2460a083b89427cffaacdbd5f707ffc/test_common/harness/compat.h#L141-L151

Unfortunately, this means we cannot use the functions std::isnan, std::isfinite, and std::isinf functions from C++11 without generating build errors on Windows only.

We should switch to the C++ versions exclusively. Failing that, we should find another way to define these aliases that doesn't preclude using the C++ versions. Maybe:

using isnan = std::isnan;
using isfinite = std::isfinite;
using isinf = std::isinf;