The header
has the following additions:
namespace std {
template<class Codecvt, class Elem = wchar_t,
class WideAlloc = allocator<Elem>,
class ByteAlloc = allocator<char>>
class wstring_convert;
template<class Codecvt, class Elem = wchar_t,
class Tr = char_traits<Elem>>
class wbuffer_convert;
}