Attached is another (independent) patch for non-ASCII characters in commands in asynchronous mode on Windows.

I still don't know how to fix the synchronous mode with output.
The commands themselves seem to be executed using a pipe. That already works with non-ASCII characters. But if the output contains non-ASCII characters, it is broken currently.

The key is probably to understand how `iprocstream` works in `run_command_and_return_output` here:
https://hg.savannah.gnu.org/hgweb/octave/file/54509b7fddd3/libinterp/corefcn/toplev.cc#l104

Can it just inherit from `std::wios` instead of `std::ios` and everything will fall in place correctly? If that is the way to go, that would probably mean a lot of duplicated classes.
Is there a better way to implement this?

(file #50362)

The function "system" doesn't work on Windows if the command that should be executed contains non-ASCII characters.

I have a partial fix almost ready that should fix this in synchronous mode without output.

I believe I also understand what is necessary to get this to work for asynchronous calls.

But I'm stuck when it comes to understanding the synchronous case with output. I don't know how to fix getting output including non-ASCII characters.
Is that done in the iprocstream class? If so, how? Any help would be appreciated.

I'll upload the partial changeset as soon as I have a bug number.