Windows/MinGW extension: opening std::fstream with a wstring/wchar_t*

[Paolo Carlini]

Hi,

to be really honest, I'm not sure I like the idea of adding all this 
code only to enable such an extension benefiting only Windows/MinGW. By 
the way, submitter himself noticed that subclassing is another viable 
option.

At minimum, let's look forward some feedback from the maintainers of the 
Cygwin / MinGW ports...

Paolo.