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/exception_pointer_unimplemented.hh

@@ -0,0 +1,68 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libcxx/stdio.h"
+#include "third_party/libcxx/stdlib.h"
+#include "third_party/libcxx/exception"
+
+namespace std {
+
+exception_ptr::~exception_ptr() _NOEXCEPT {
+  // #warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+}
+
+exception_ptr::exception_ptr(const exception_ptr& other) _NOEXCEPT
+    : __ptr_(other.__ptr_) {
+  // #warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+}
+
+exception_ptr& exception_ptr::operator=(const exception_ptr& other) _NOEXCEPT {
+  // #warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+}
+
+nested_exception::nested_exception() _NOEXCEPT : __ptr_(current_exception()) {}
+
+#if !defined(__GLIBCXX__)
+
+nested_exception::~nested_exception() _NOEXCEPT {}
+
+#endif
+
+_LIBCPP_NORETURN
+void nested_exception::rethrow_nested() const {
+  // #warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+#if 0
+  if (__ptr_ == nullptr)
+      terminate();
+  rethrow_exception(__ptr_);
+#endif // FIXME
+}
+
+exception_ptr current_exception() _NOEXCEPT {
+  // #warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+}
+
+_LIBCPP_NORETURN
+void rethrow_exception(exception_ptr p) {
+  // #warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+}
+
+} // namespace std