Eigen: Fix MSVC C++17 language standard detection logic

To detect C++17 support, use _MSVC_LANG macro instead of _MSC_VER. _MSC_VER can indicate whether the current compiler version could support the C++17 language standard, but not whether that standard is actually selected (i.e. via /std:c++17).
See these web pages for more details:
https://devblogs.microsoft.com/cppblog/msvc-now-correctly-reports-__cplusplus/
https://docs.microsoft.com/en-us/cpp/preprocessor/predefined-macros

0 files changed, 0 insertions, 0 deletions