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.

tool/emacs/c.lang

@@ -102,7 +102,7 @@ Keywords={
 "decltype",
 "forceinline",
 "nocallersavedregisters",
-"nothrow",
+"dontthrow",
 "nooptimize",
 "optimizesize",
 "optimizespeed",
@@ -132,7 +132,7 @@ Keywords={
 "warnifused",
 "attributeallocsize",
 "attributeallocalign",
-"nodiscard",
+"dontdiscard",
 "nointerpose",
 "compatfn",
 "returnsnonnull",