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/cosmo-c-keywords.el

@@ -46,7 +46,7 @@
            "decltype"
            "forceinline"
            "nocallersavedregisters"
-           "nothrow"
+           "dontthrow"
            "nooptimize"
            "optimizesize"
            "optimizespeed"
@@ -79,7 +79,7 @@
            "warnifused"
            "attributeallocsize"
            "attributeallocalign"
-           "nodiscard"
+           "dontdiscard"
            "nointerpose"
            "compatfn"
            "returnsnonnull"