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/viz/int2float.c

@@ -29,10 +29,10 @@ double b64;
 long double b80;
 uint32_t u32;
 uint64_t u64;
-intmax_t x;
+int128_t x;
 
 void int2float(const char *s) {
-  x = strtoimax(s, NULL, 0);
+  x = strtoi128(s, NULL, 0);
   if ((0 <= x && x <= UINT32_MAX) && !startswith(s, "-") &&
       (!endswith(s, "l") && !endswith(s, "L"))) {
     u32 = x;