Update limits.cc to C++20 version

Author: chris-durand

src/limits.cc

@@ -1,6 +1,6 @@
 // Static data members of -*- C++ -*- numeric_limits classes
 
-// Copyright (C) 1999-2018 Free Software Foundation, Inc.
+// Copyright (C) 1999-2020 Free Software Foundation, Inc.
 //
 // This file is part of the GNU ISO C++ Library.  This library is free
 // software; you can redistribute it and/or modify it under the
@@ -525,6 +525,33 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   const bool numeric_limits<long double>::tinyness_before;
   const float_round_style numeric_limits<long double>::round_style;
 
+#ifdef _GLIBCXX_USE_CHAR8_T
+  // char8_t
+  const bool numeric_limits<char8_t>::is_specialized;
+  const int  numeric_limits<char8_t>::digits;
+  const int  numeric_limits<char8_t>::digits10;
+  const int  numeric_limits<char8_t>::max_digits10;
+  const bool numeric_limits<char8_t>::is_signed;
+  const bool numeric_limits<char8_t>::is_integer;
+  const bool numeric_limits<char8_t>::is_exact;
+  const int  numeric_limits<char8_t>::radix;
+  const int  numeric_limits<char8_t>::min_exponent;
+  const int  numeric_limits<char8_t>::min_exponent10;
+  const int  numeric_limits<char8_t>::max_exponent;
+  const int  numeric_limits<char8_t>::max_exponent10;
+  const bool numeric_limits<char8_t>::has_infinity;
+  const bool numeric_limits<char8_t>::has_quiet_NaN;
+  const bool numeric_limits<char8_t>::has_signaling_NaN;
+  const float_denorm_style numeric_limits<char8_t>::has_denorm;
+  const bool numeric_limits<char8_t>::has_denorm_loss;
+  const bool numeric_limits<char8_t>::is_iec559;
+  const bool numeric_limits<char8_t>::is_bounded;
+  const bool numeric_limits<char8_t>::is_modulo;
+  const bool numeric_limits<char8_t>::traps;
+  const bool numeric_limits<char8_t>::tinyness_before;
+  const float_round_style numeric_limits<char8_t>::round_style;
+#endif // _GLIBCXX_USE_CHAR8_T
+
   // char16_t
   const bool numeric_limits<char16_t>::is_specialized;
   const int  numeric_limits<char16_t>::digits;