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.

libc/stdio/printf.c

@@ -22,9 +22,9 @@
  * Formats and writes string to stdout.
  *
  * Cosmopolitan supports most of the standard formatting behaviors
- * described by `man 3 printf`, in addition to the following:
+ * described by `man 3 printf`, in addition to the following
  *
- * - `%jd`, `%jx`, etc. are {,u}intmax_t which in Cosmopolitan is 128-bit.
+ * - `%jjd`, `%jjx`, etc. are {,u}int128_t (cosmopolitan only)
  *
  * - `%'d` or `%,d` may be used to insert thousands separators. The prior is
  *   consistent with C; the latter is consistent with Python.