[SDL] Unicode wm caption

[Ryan C. Gordon]

> Sam, can Unicode caption support be made as an optional compilation switch in a
> future release?

In theory, you should always be giving SDL strings in UTF-8 encoding, 
and it will deal with making them "Unicode" behind the scenes (or 
dithering them to the correct codepage--or maybe just '?' chars--for 
win9x systems.

It's possible that we don't handle this correctly for window captions on 
Win32, though and are using the "Ansi" win32 entry point...if that's the 
case, it's a bug and we'll fix it.

--ryan.