Missing Unicode support in Win32 implementation.

[qis]

Setting UNICODE/_UNICODE breaks the library because it expects e.g. CreateDirectoryA instead of CreateDirectoryW.

[mosra]

Yes, I'm aware of this one -- more details in mosra/magnum#98.

Question: do you need Unicode support now? For now I propose to fix this with using the *A functions directly and proper Unicode-aware implementation will appear later, if that would be okay for you.

[qis]

I just started looking at it all and this was the first issue to come up. There is no hurry. Personally, I'm happy with std::experimental::filesystem but that would be inconvenient for most others.

[mosra]

So in the end I went fully on it. Was quite a lot harder than I originally thought, mainly because MinGW is such a special snowflake. Gah.

• Full UTF-8 support in Utility::Directory on Windows is done in a1061d0
• Opening UTF-8 filenames in Utility::Configuration on Windows is done in f2a9f1c
• Handling of UTF-8 environment variables in Utility::Arguments on Windows is done in 49be6d0
• Ability to use PluginManager with UTF-8 paths on Windows is done in 2328ba3
• UTF-8 filenames are passable to corrade_add_resource() since b90f5b4

If you encounter any problems (I hope not, as I tried to increase the test coverage to cover these cases), please report ;)

[qis]

@mosra Amazing work, thanks!