Modernize our usage of type_traits

[sloriot]

use std::enable_if_t, _v suffix, ....

[sloriot]

@mglisse I did it by hand.

[afabri]

The ICE of VCV2015 comes probably from the fact that you use C++17 in <CGAL/type_traits/is_iterator.h>

[sloriot]

I don't, I'm using CGAL_CPP17_INLINE which is empty if Cpp17 is not used...

[lrineau]

I don't, I'm using CGAL_CPP17_INLINE which is empty if Cpp17 is not used...

Sébastien is right. Variable templates are a C++14 feature. I mixed it up with C++17, because their usage in the STL, like std::is_same_v, have been introduced only in C++17, probably because of the lack of inline variables (only since C++17).

[sloriot]

Still failing in CGAL-5.6-Ic-26 on MSVC2015. See here for example.

[sloriot]

@afabri would you find some time to see if we can work around the issue on MSVC2015?

[sloriot]

Successfully tested in CGAL-5.6-Ic-46!