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/chibicc/parse.c

@@ -555,7 +555,7 @@ static Token *thing_attributes(Token *tok, void *arg) {
       consume_attribute(&tok, tok, "warn_unused_result") ||
       consume_attribute(&tok, tok, "flatten") ||
       consume_attribute(&tok, tok, "leaf") ||
-      consume_attribute(&tok, tok, "nothrow") ||
+      consume_attribute(&tok, tok, "dontthrow") ||
       consume_attribute(&tok, tok, "optnone") ||
       consume_attribute(&tok, tok, "returns_twice") ||
       consume_attribute(&tok, tok, "nodebug") ||