wrong usage of ios_base::narrow

[vandrejev]

/cvsroot/boost/boost/boost/date_time/date_parsing.hpp 
revision 1.18, lines 207, 214

std::stringstream has char_type typedef evidently equal 
to char, not wchar_t, so in std::stringstream::narrow 
function the first argument has type char and in the call

ss << ss.narrow(*beg++, 'X');

*beg will be converted from wchar_t to char before call 
to narrow will be made.

I suggest the following patch:

diff -c -r1.18 date_parsing.hpp
***************
*** 207,214 ****
                                 wchar_t) 
      {
        std::stringstream ss("");
        while(beg != end) {
!         ss << ss.narrow(*beg++, 'X'); // 'X' will cause 
exception to be thrown
        }
        return parse_date<date_type>(ss.str());
      }
--- 207,215 ----
                                 wchar_t) 
      {
        std::stringstream ss("");
+       std::locale loc;
        while(beg != end) {
!         ss << std::use_facet<std::ctype<wchar_t> >
(loc).narrow(*beg++, 'X');
        }
        return parse_date<date_type>(ss.str());
      }