[boost] std::wstring support in GCC/Cygwin?

What is the story on std::wstring support with GCC/Cygwin? How do you turn it on? I'm trying to test the Boost.Filesystem i18n branch with more compilers. It is working fine with last model Intel, Metrowerks, and Microsoft on Windows, and GCC on the Mac, but no luck with GCC/Cygwin. --Beman