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/build/runit.c

@@ -139,7 +139,8 @@ void CheckExists(const char *path) {
   }
 }
 
-nodiscard char *MakeDeployScript(struct addrinfo *remotenic, size_t combytes) {
+dontdiscard char *MakeDeployScript(struct addrinfo *remotenic,
+                                   size_t combytes) {
   const char *ip4 = (const char *)&remotenic->ai_addr4->sin_addr;
   return xasprintf("mkdir -p o/ && "
                    "dd bs=%zu count=%zu of=o/runitd.$$.com 2>/dev/null && "