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/mkostempsm.c

@@ -74,8 +74,8 @@ static uint64_t g_mkostemps_reseed;
  *     or -1 w/ errno
  * @see kTmpPath
  */
-nodiscard int mkostempsm(char *template, int suffixlen, unsigned flags,
-                         int mode) {
+dontdiscard int mkostempsm(char *template, int suffixlen, unsigned flags,
+                           int mode) {
   if (g_mkostemps_reseed++ % RESEED == 0) g_mkostemps_rand = rand64();
   return mkostempsmi(template, suffixlen, flags, &g_mkostemps_rand, mode, open);
 }