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/calls/creat.c

@@ -35,6 +35,6 @@
  * @see open(), touch()
  * @asyncsignalsafe
  */
-nodiscard int creat(const char *file, uint32_t mode) {
+dontdiscard int creat(const char *file, uint32_t mode) {
   return openat(AT_FDCWD, file, O_CREAT | O_WRONLY | O_TRUNC, mode);
 }