New test 22_locale/collate_wchar_t_members.cc fails on cygwin

[Benjamin Kosnik]

Ack, sorry about this.

> problem seems to be:
>  `wstring' undeclared (first use this function)
> 
> >From libstdc++-v3/include/bits/stringfwd.h it seems that defining
> _GLIBCPP_USE_WCHAR_T may fix this.  Is this a "good thing"?  If so, how do I
> do it?

#ifdef _GLIBCPP_USE_WCHAR_T
test
#endif

like libstdc++-v3/testsuite/22_locale/codecvt_wchar_t_char.cc 

I'll do it tonight.

-benjamin