nanoflann.hpp can not compile use vs2015

[GaianRan]

Describe the bug

when i complie CCCoreLib sourcecode with vs2015 ,the file nanoflann.hpp can not pass , the following line cannot pass: 664 typename std::underlying_type::type;
error C2899: typename cannot be used outside a template declaration i think this error maybe from VC++,so i want to know what is the lowest VC version for this project How to reproduce

Expected behaviour

Additional context

Your environment

• CCCoreLib Version (or git hash/tag):
• OS & Version:
• Qt Version (if compiling w/Qt):
• TBB Version (if compiling w/TBB):

[dgirardeau]

Yep, probably an issue with Visual 2015. You should use 2017 at minimum.