Allow UTF-8 console output on Windows (for -console)

[Daaaav]

Changes:

Right now, Windows assumes all our console output is code page ????. That means our UTF-8 output appears mangled. (I ran into this while testing IME text input by outputting strings to the console)

For a moment I was scared we'd need to do UTF-16 conversions and call Windows-specific print functions like WriteConsoleW() in our vlog functions, but fortunately SetConsoleOutputCP(CP_UTF8) works just fine.

Example of vlog_warn(loc::gettext("return")) in German (just to make sure the encoding of the source file is not a factor) before this change:

After:

Legal Stuff:

By submitting this pull request, I confirm that...

• [x] My changes may be used in a future commercial release of VVVVVV
• [x] I will be credited in a CONTRIBUTORS file and the "GitHub Friends" section of the credits for all of said releases, but will NOT be compensated for these changes

[Daaaav]

I'm not sure I really agree there to be honest - it doesn't seem critical and "alarm-worthy" if for example some older version of Windows only supports legacy console output (what's the user gonna do about it?) and for nearly all of our output it wouldn't make a difference since it's still in English. Adding an error check there does make the code a little less clean, and I don't think error checks being needed for some functions necessarily makes them needed for all functions.

If you'd like me to do it anyway, just say so.

[InfoTeddy]

Yes, add the check.

It's not alarm-worthy, but it's at least a warning. And it should be there to make it clear to the user that it's not our fault if UTF-8 output is mangled.

[Daaaav]

Okay well... For the error message to even show up, I had to move it down further, because there's no console output visible before the freopens. Furthermore, the message will be hidden away by all the other output (like the Viridian) because the window will scroll down instantly. Either way, done.