[Bug 51346] x264guiEx partly shows white box characters when using Wine-Mono (default encoding issue with C++/CLI).

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=51346

--- Comment #3 from Esme Povirk  ---
Despite the documentation, the implementation does not depend on
Encoding.Default:
https://github.com/mono/corefx/blob/9174bbeb7e1e4d3dc51f4f82243cbf4c62c61efa...

There is already an implementation based on CP_ACP, but I guess Mono takes the
!PLATFORM_WINDOWS path which hard-codes UTF8. I haven't needed to fork corefx
yet, and I'd like to continue to avoid that if I can. Maybe I can get away with
defining PLATFORM_WINDOWS for the win32 mscorlib.dll, it doesn't seem to be
used in many places. It would also change event logging to use win32.