Fix for Windows and CPP17 compatibility

[raymondyfei]

• Member initializer is a C++20 feature. However, as suggested by the VFX reference platform, many toolchains still use C++17. In this PR, we make the code C++17 compatible.
• Fixed a "divide by zero" compilation error on MSVC/VS2022 on Windows.
• Fixed a missing header for std::sort and function Quat4f times(const Quat4f &a, const Quat4f &b) cannot return a constexpr with MSVC compiler.

[fortmeier]

nearly works for me with MSVC/VS2022: I need to add

#define _USE_MATH_DEFINES
#include "math.h"

in splat-types.h to make it work

[raymondyfei]

nearly works for me with MSVC/VS2022: I need to add

#define _USE_MATH_DEFINES #include "math.h"

in splat-types.h to make it work

@fortmeier Thanks for the suggestion! Added to my branch.