message: Force RANGES_NO_STD_FORWARD_DECLARATIONS when _GLIBCXX_DEBUG is defined
  Fixes
diff: @@ -110,6 +110,13 @@ namespace ranges
  #ifdef _LIBCPP_VERSION
  #define RANGES_BEGIN_NAMESPACE_STD _LIBCPP_BEGIN_NAMESPACE_STD
  #define RANGES_END_NAMESPACE_STD _LIBCPP_END_NAMESPACE_STD
  +#elif defined(_MSVC_STL_VERSION)
  +#define RANGES_BEGIN_NAMESPACE_STD _STD_BEGIN
  +#define RANGES_END_NAMESPACE_STD _STD_END
  +#elif defined(_GLIBCXX_DEBUG)
  +#ifndef RANGES_NO_STD_FORWARD_DECLARATIONS
  +#define RANGES_NO_STD_FORWARD_DECLARATIONS
  +#endif
  #else
  #define RANGES_BEGIN_NAMESPACE_STD namespace std {
  #define RANGES_END_NAMESPACE_STD }
  