[c++] wchar_t instantiations missing now

[Benjamin Kosnik]

> You must be configuring in some peculiar way, since we're now using
> stdio by default, and since that doesn't provide wide-character
> support, right? :-)

It's a build w/ libio still on, but I too believe it to be a bug with the 
new ABI. After all, wchar_t should work.

--enable-cstdio=libio 

Is the only configuration hackery in my build tree.

thanks,
benjamin