_XOPEN_SOURCE problem?

[Phil Nelson <phil%NetBSD.org@localhost>]

Hello,

   I ran into a problem compiling a program that used _XOPEN_SOURCE
definitions with g++.   I've distilled the problem down to the following
program:

------ junk.cpp

#define _XOPEN_SOURCE 600
#include <string>

int main()
{
  return 0;
}

------

(You actually get the same compile problem by using just the first
two lines ...)

And this is the compile problem.  

$ g++ junk.cpp
In file included from /usr/include/g++/bits/postypes.h:42:0,
                 from /usr/include/g++/bits/char_traits.h:42,
                 from /usr/include/g++/string:42,
                 from junk.cpp:2:
/usr/include/g++/cwchar:166:11: error: '::vfwscanf' has not been declared
/usr/include/g++/cwchar:172:11: error: '::vswscanf' has not been declared
/usr/include/g++/cwchar:176:11: error: '::vwscanf' has not been declared
/usr/include/g++/cwchar:193:11: error: '::wcstof' has not been declared

I'm presuming this should not be generating these errors.   There isn't
a PR on this topic.   I can file a PR if needed.

--Phil