A couple of small fixes for C++20 compliance

[moxian]

Summary

None

Purpose of change

I tried compiling our codebase with --std=c++-20 and it almost worked, modulo these few issues (and the char8_t thing which we don't talk about).
So I thought I'd upstream them, should be easy enough.

Describe the solution

Set c++ standard to c++20 in MSVS, add a /Zc:char8_t- to additional compilation options, build the thing, fix errors as you get them

Describe alternatives you've considered

N/A

Testing

Builds. Old saves load fine.

Additional context

N/A