Import C++ Standard Template Library

You can now use the hardest fastest and most dangerous language there is
with Cosmopolitan. So far about 75% of LLVM libcxx has been added. A few
breaking changes needed to be made to help this go smoothly.

- Rename nothrow to dontthrow
- Rename nodiscard to dontdiscard
- Add some libm functions, e.g. lgamma, nan, etc.
- Change intmax_t from int128 to int64 like everything else
- Introduce %jjd formatting directive for int128_t
- Introduce strtoi128(), strtou128(), etc.
- Rename bsrmax() to bsr128()

Some of the templates that should be working currently are std::vector,
std::string, std::map, std::set, std::deque, etc.

third_party/libcxx/locale.h

@@ -0,0 +1,44 @@
+// -*- C++ -*-
+//===---------------------------- locale.h --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_LOCALE_H
+#define _LIBCPP_LOCALE_H
+
+/*
+    locale.h synopsis
+
+Macros:
+
+    LC_ALL
+    LC_COLLATE
+    LC_CTYPE
+    LC_MONETARY
+    LC_NUMERIC
+    LC_TIME
+
+Types:
+
+    lconv
+
+Functions:
+
+   setlocale
+   localeconv
+
+*/
+
+#include "third_party/libcxx/__config"
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+#include "libc/isystem/locale.h"
+
+#endif // _LIBCPP_LOCALE_H