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/decode/zip.c

@@ -46,12 +46,12 @@
  * @fileoverview Zip File Disassembler.
  */
 
-nodiscard char *FormatDosDate(uint16_t dosdate) {
+dontdiscard char *FormatDosDate(uint16_t dosdate) {
   return xasprintf("%04u-%02u-%02u", ((dosdate >> 9) & 0b1111111) + 1980,
                    (dosdate >> 5) & 0b1111, dosdate & 0b11111);
 }
 
-nodiscard char *FormatDosTime(uint16_t dostime) {
+dontdiscard char *FormatDosTime(uint16_t dostime) {
   return xasprintf("%02u:%02u:%02u", (dostime >> 11) & 0b11111,
                    (dostime >> 5) & 0b111111, (dostime << 1) & 0b111110);
 }