Remove `#ifdef` catering to MSVC 2012 and earlier in `math_funcs.h`
Remove `#ifdef` catering to MSVC 2012 and earlier in `math_funcs.h`

For the `master` branch, the minimum supported MSVC version is now
MSVC 2017 (with MSVC 2019 being recommended).

(cherry picked from commit b57d9c8005067d149fe34392b19a0520352cd5c6)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot