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.

build/definitions.mk

@@ -149,7 +149,6 @@ DEFAULT_CFLAGS =							\
 	-std=gnu2x
 
 DEFAULT_CXXFLAGS =							\
-	-std=gnu++11							\
 	-fno-rtti							\
 	-fno-exceptions							\
 	-fuse-cxa-atexit						\