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.

third_party/gdtoa/gdtoa.h

@@ -92,6 +92,10 @@ int strtopxL(const char *, char **, void *);
 #define strtopxL(s, se, x) strtorxL(s, se, 1, x)
 #endif
 
+float wcstof(const wchar_t *, wchar_t **);
+double wcstod(const wchar_t *, wchar_t **);
+long double wcstold(const wchar_t *, wchar_t **);
+
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
 #endif /* COSMOPOLITAN_THIRD_PARTY_GDTOA_GDTOA_H_ */